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Sample records for coulometry

  1. Impact electrochemistry: colloidal metal sulfide detection by cathodic particle coulometry.

    Science.gov (United States)

    Lim, Chee Shan; Pumera, Martin

    2015-10-28

    The determination of the size and concentration of colloidal nano and microparticles is of paramount importance to modern nanoscience. Application of the particle collision technique on metal and metal oxide nanoparticles has been intensively explored over the past decade owing to its ability to determine the particle size and concentration via reactions including the inherent oxidation or the reduction of nanoparticles as well as surface reactions catalysed by the nanoparticles. Transition metal dichalcogenide particles were previously quantified using the anodic (oxidative) particle coulometry method. Here we show that cathodic (reductive) particle coulometry can be favorably used for the detection of metal sulfide colloidal particles. The detection of sulfides of cobalt and lead was performed using the particle collision technique in this work. The presence of spikes confirmed the viability of detecting new and larger particles from compounds using reductive (cathodic) potentials. Such an expansion of the impact particle coulometry method will be useful and applicable to the determination of concentration and size of colloidal metal sulfide nanoparticles in general.

  2. Plutonium analysis from controlled-potential coulometry for the certification of the MP3 standard material

    Energy Technology Data Exchange (ETDEWEB)

    Ruas, A.; Dalier, V.; Pivato, J. [CEA-Marcoule BP 17171 30207 Bagnols-sur-Ceze Cedex (France)

    2008-07-01

    Coulometry is an assay method in which the quantity of the element analyzed is determined by measuring a quantity of electricity. For contributing to the certification of the new metal plutonium reference material (MP3), controlled-potential coulometry (CPC) has many advantages: it is a high accuracy absolute chemical analysis technique. Many studies are now conducted on plutonium solutions, to improve the operating conditions and the current apparatus, for mass determination with a precision of 0.1%. The different experimental preliminary results are discussed and the apparatus described. The coulometry cell assembly comprises a motor connected to a stirrer designed to prevent splashing, an inlet tube for inert gas, three electrodes, and a thermocouple for measuring the temperature. The measuring system includes a potentiostat, a CPU, a calibrated current generator, a temperature indicator and a voltmeter, all maintained at a constant temperature. Current integration is made by electronic components, introduced in the potentiostat and the CPU. (authors)

  3. Progress in Karl Fischer coulometry using diaphragm-free cells.

    Science.gov (United States)

    Cedergren, A; Jonsson, S

    2001-11-15

    Different designs of a semiopen, drainable cathode compartment of a medium-sized coulometric Karl Fischer (KF) cell for the determination of water in the range 0.1-500 microg were evaluated. The main criterion for the design was to keep the resistance between the anolyte and catholyte low enough to permit the generation of currents larger than 20 mA (for an output voltage of 28 V). It was found that a good compromise between the size of this current and a minimal influence from diffusing/migrating oxidizable reduction products from the catholyte was achieved by means of an interface having a channel length and diameter of 8 and 2.1 mm, respectively (catholyte volume, approximately 1 mL). To show the general applicability of the concept, the following different types of coulometric reagents suitable for nonpolar and polar samples, as well as for samples containing active carbonyl compounds, were investigated: Hydranal Coulomat A, AD, AK, AG-H (modified with chloroform, Merck), and two homemade methanolic reagents modified with 40% (v/v) chloroform and 50% (v/v) formamide, respectively. Except for Hydranal Coulomat A, the mean value of five consecutive titrations of 50 microg water did not deviate by more than 0.2% from the expected value for all reagents. Draining after every titration was sufficient to obtain accurate results, even for Coulomat A which, when used in the commercial diaphragm-free system of Metrohm, gave values which were about 10% too high. As compared to earlier reported results for diaphragm-free coulometry, the descibed modified cell represents a significant improvement, mainly because of the high accuracy achieved for all types of reagents.

  4. Thickness measurement of Sn-Ag hot dip coatings on Large Hadron Collider Superconducting strands by coulometry

    CERN Document Server

    Arnau-Izquierdo, G; Oberli, L R; Scheuerlein, C; Taborelli, M; 10.1149/1.1715094

    2004-01-01

    Amperostatic coulometry is applied for the thickness measurement of Sn-Ag hot dip coatings, which comprise an extended Sn-Cu interdiffusion layer. Complementary measurements, notably weight loss, X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), X-ray fluorescence (XRF) and dynamic secondary ion mass spectroscopy (DSIMS) have been performed in order to obtain a better interpretation of the coulometry results. Based on the experimental results presented in this article the three potential changes that are observed during coulometry measurements are ascribed to (1) the entire dissolution of pure Sn, (2) the formation of a CuCl salt layer and (3) the surface passivation. The measurement of the pure Sn mass is well reproducible despite of strong coating thickness variations that are detected by XRF. Several experimental problems, in particular a coating undercutting, hamper the determination of the Sn mass in the intermetallic Sn-Cu layer.

  5. Thickness measurement of Sn-Ag hot dip coatings on Large Hadron Collider Superconducting strands by coulometry

    CERN Document Server

    Scheuerlein, C; Arnau-Izquierdo, G; Oberli, L R; Taborelli, M; 10.1149/1.1715094

    2004-01-01

    Amperostatic coulometry was applied for the thickness measurement of Sn-Ag hot dip coatings, which comprise an extended Sn-Cu interdiffusion layer. Complementary measurements, notably weight loss, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, X-ray fluorescence (XRF), and dynamic secondary ion mass spectroscopy were performed in order to obtain a better interpretation of the coulometry results. Based on the experimental results presented in this article, the three potential changes observed during coulometry measurements are ascribed to (i) the entire dissolution of pure Sn, (ii) the formation of a CuCl salt layer, and (iii) the surface passivation. The measurement of the pure Sn mass is well reproducible despite strong coating thickness variations detected by XRF. Several experimental problems, in particular, a coating undercutting, hamper the determination of the Sn mass in the intermetallic Sn-Cu layer. (19 refs).

  6. Progress in pulsed-current Karl Fischer coulometry using diaphragm-free cells.

    Science.gov (United States)

    Nordmark, U; Cedergren, A

    2000-07-01

    Factors influencing the accuracy of water determinations using diaphragm-free, pulsed current Karl Fischer (KF) coulometry were investigated with the new Metrohm 756 instrument. Results obtained with commercially available reagents from Riedel-deHaen and Merck were compared with home-made ones that were especially designed to minimize the formation of iodine-consuming reduction products generated in the cathode reaction. Positive errors in the range 2-5% were found for the commercial reagents as compared to 0.2-1% for the home-made ones which were buffered at about pH 10 containing modifiers like chloroform, hexanol or ethylene glycol. Except for the composition of the KF-reagent, the cathode current density and the titration rate were found to be critical parameters for the accuracy of the determinations. For all reagents investigated, the best results were obtained for the maximum generator current 400 mA (corresponding to a current density of 1,400 mA cm(-2)) in combination with a maximum titration rate of 2,000 microg min(-1). Surprisingly, the errors found under optimum conditions for the pulse technique were always somewhat larger than the corresponding values obtained with continuous coulometry.

  7. Surfactant media for constant-current coulometry. Application for the determination of antioxidants in pharmaceuticals

    Energy Technology Data Exchange (ETDEWEB)

    Ziyatdinova, Guzel, E-mail: Ziyatdinovag@mail.ru [Analytical Chemistry Department, A.M. Butlerov Institute of Chemistry, Kazan (Volga Region) Federal University, Kremlyevskaya, 18, Kazan 420008 (Russian Federation); Ziganshina, Endzhe; Budnikov, Herman [Analytical Chemistry Department, A.M. Butlerov Institute of Chemistry, Kazan (Volga Region) Federal University, Kremlyevskaya, 18, Kazan 420008 (Russian Federation)

    2012-09-26

    Highlights: Black-Right-Pointing-Pointer Applicability of surfactants in constant-current coulometry is shown for the first time. Black-Right-Pointing-Pointer Reactions of antioxidants with electrogenerated titrants in surfactant media are investigated. Black-Right-Pointing-Pointer Water insoluble antioxidants can be determined in water media with addition of surfactants. Black-Right-Pointing-Pointer Coulometric determination of antioxidants in pharmaceutical dosage forms using surfactants media is developed. - Abstract: Effect of surfactant presence on electrochemical generation of titrants has been evaluated and discussed for the first time. Cationic (1-dodecylpyridinium and cetylpyridinium bromide), anionic (sodium dodecyl sulfate) and nonionic (Triton X100 and Brij{sup Registered-Sign} 35) surfactants as well as nonionic high molecular weight polymer (PEG 4000) do not react with the electrogenerated bromine, iodine and hexacyanoferrate(III) ions. The electrogenerated chlorine chemically interact with Triton X100 and Brij{sup Registered-Sign} 35. The allowable range of surfactants concentrations providing 100% current yield has been found. Chain-breaking low molecular weight antioxidants (ascorbic acid, rutin, {alpha}-tocopherol and retinol) were determined by reaction with the electrogenerated titrants in surfactant media. Nonionic and cationic surfactants can be used for the determination of antioxidants by reaction with the electrogenerated halogens. On contrary, cationic surfactants gives significantly overstated results of antioxidants determination with electrogenerated hexacyanoferrate(III) ions. The use of surfactants in coulometry of {alpha}-tocopherol and retinol provides their solubilization and allows to perform titration in water media. Simple, express and reliable coulometric approach for determination of {alpha}-tocopherol, rutin and ascorbic acid in pharmaceuticals using surfactant media has been developed. The relative standard deviation of the

  8. Potentiometric determination of the total acidity of humic acids by constant-current coulometry.

    Science.gov (United States)

    Palladino, Giuseppe; Ferri, Diego; Manfredi, Carla; Vasca, Ermanno

    2007-01-16

    A straightforward method for both the quantitative and the equilibrium analysis of humic acids in solution, based on the combination of potentiometry with coulometry, is presented. The method is based on potentiometric titrations of alkaline solutions containing, besides the humic acid sample, also NaClO(4) 1M; by means of constant current coulometry the analytical acidity in the solutions is increased with a high precision, until the formation of a solid phase occurs. Hence, the total acid content of the macromolecules may be determined from the e.m.f. data by using modified Gran plots or least-squares sum minimization programs as well. It is proposed to use the pK(w) value in the ionic medium as a check of the correctness of each experiment; this datum may be readily obtained as a side-result in each titration. Modelling acid-base equilibria of the HA samples analysed was also performed, on the basis of the buffer capacity variations occurring during each titration. The experimental data fit, having the least standard deviation, was obtained assuming a mixture of three monoprotic acids (HX, HY, HZ) having about the same analytical concentration, whose acid dissociation constants in NaClO(4) 1M at 25 degrees C were pK(HX)=3.9+/-0.2, pK(HY)=7.5+/-0.3, pK(HZ)=9.5+/-0.2, respectively. With the proposed method the handling of alkaline HA solutions, the titration with very dilute NaOH or HCl solutions and the need for the availability of very small volumes of titrant to be added by microburettes may be avoided.

  9. Certification of the reference material of water content in water saturated 1-octanol by Karl Fischer coulometry, Karl Fischer volumetry and quantitative nuclear magnetic resonance.

    Science.gov (United States)

    Wang, Haifeng; Ma, Kang; Zhang, Wei; Li, Jia; Sun, Guohua; Li, Hongmei

    2012-10-15

    Certified reference materials (CRMs) of water content are widely used in the calibration and validation of Karl Fischer coulometry and volumetry. In this study, the water content of the water saturated 1-octanol (WSO) CRM was certified by Karl Fischer coulometry, volumetry and quantitative nuclear magnetic resonance (Q NMR). The water content recovery by coulometry was 99.76% with a diaphragm-less electrode and Coulomat AG anolyte. The relative bias between the coulometry and volumetry results was 0.06%. In Q NMR, the water content of WSO is traceable to the International System (SI) of units through the purity of internal standard. The relative bias of water content in WSO between Q NMR and volumetry was 0.50%. The consistency of results for these three independent methods improves the accuracy of the certification of the RM. The certified water content of the WSO CRM was 4.76% with an expanded uncertainty of 0.09%.

  10. Anodic passivation of tin by alkanethiol self-assembled monolayers examined by cyclic voltammetry and coulometry.

    Science.gov (United States)

    Worley, Barrett C; Ricks, William A; Prendergast, Michael P; Gregory, Brian W; Collins, Ross; Cassimus, John J; Thompson, Raymond G

    2013-10-22

    The self-assembly of medium chain length alkanethiol monolayers on polycrystalline Sn electrodes has been investigated by cyclic voltammetry and coulometry. These studies have been performed in order to ascertain the conditions under which their oxidative deposition can be achieved directly on the oxide-free Sn surface, and the extent to which these electrochemically prepared self-assembled monolayers (SAMs) act as barriers to surface oxide growth. This work has shown that the potentials for their oxidative deposition are more cathodic (by 100-200 mV) than those for Sn surface oxidation and that the passivating abilities of these SAMs improve with increasing film thickness (or chain length). Oxidative desorption potentials for these films have been observed to shift more positively, and in a highly linear fashion, with increasing film thickness (~75 mV/CH2). Although reductive desorption potentials for the SAMs are in close proximity to those for reduction of the surface oxide (SnOx), little or no SnOx formation occurs unless the potential is made sufficiently anodic that the monolayers start to be removed oxidatively. Our coulometric data indicate that the charge involved with alkanethiol reductive desorption or oxidative deposition is consistent with the formation of a close-packed monolayer, given uncertainties attributable to surface roughness and heterogeneity phenomena. These experiments also reveal that the quantity of charge passed during oxidative desorption is significantly larger than what would be predicted for simple alkylsulfinate or alkylsulfonate formation, suggesting that oxidative removal involves a more complex oxidation mechanism. Analogous chronocoulometric experiments for short-chain alkanethiols on polycrystalline Au electrodes have evidenced similar oxidative charge densities. This implies that the mechanism for oxidative desorption on both surfaces may be very similar, despite the significant differences in the inherent dissolution

  11. Conditions for accurate Karl Fischer coulometry using diaphragm-free cells.

    Science.gov (United States)

    Nordmark, U; Cedergren, A

    2000-01-01

    Factors influencing the extent of formation of oxidizable reduction products in coulometric cells used for Karl Fischer (KF) determination of water were investigated. For methanolic KF reagents buffered with imidazole (Im) or diethanolamine (DEA) (separately or in combination), three parameters were found to be of outmost importance: the cathodic current density, the pH, and the concentration of protonated base (ImH+ or DEAH+). For reagents buffered with only Im, the relative formation of oxidizable reduction products varied in the range 2-40%; i.e., 51-70 micrograms of water was found for a 50 micrograms water sample, depending on the above-mentioned parameters. The lowest values were observed for reagents having a pH around 10 in combination with cathodic current densities in the range 2000-5000 mA cm-2. For all the Imbuffered reagents investigated, the addition of modifiers such as chloroform, hexanol, and carbon tetrachloride was found to decrease the formation of oxidizable reduction products significantly. For example, a reagent buffered at pH 10 containing 1 M hexanol gave less than 0.3% formation in the current density interval from 200 to 4000 mA cm-2. The best reagents based on the above-mentioned modifiers were tested in the continuous coulometric mode with errors typically in the interval 0-0.5% using optimum conditions. One prerequisite for obtaining such small errors with diaphragm-free continuous coulometry is to use a cathode area no larger than 0.002 cm2. For some of the reagents based on both Im and DEA, the formation of oxidizable reduction products was close to zero at certain current densities, although the analytical performance was not as good as for the reagents buffered solely by Im due to longer conditioning and titration times.

  12. Determination of kinetics of the karl Fischer reaction based on coulometry and true potentiometry.

    Science.gov (United States)

    Cedergren, A

    1996-03-01

    A new measurement technique based on a combination of coulometry and zero-current potentiometry is described for determination of the kinetics of rapidly reacting Karl Fischer (KF) reagents. This makes it possible to determine the order as well as the rate constant for large variations in the concentrations of iodine and water present during a titration. It was shown that for imidazole-based methanolic reagents exposed to a large variation in the concentration of water, the KF reaction is first order with respect to iodine, sulfur dioxide, and water only for reagents in which the concentration of nonprotonated imidazole is very low. The rate constant determined for such a reagent (1 M imidazole, 0.8 M sulfur dioxide, 0.1 M iodine) was equal to that reported earlier in the literature. Regions showing first-order kinetics were also found for low concentrations of water when imidazole concentrations up to 2 mol/L were used, provided that these reagents had a quotient [Im](free)/[ImH(+)] around 4. In the interval 2-8 mol/L of imidazole, the order of the reaction with respect to iodine was, in most cases, one-half, while it was changed to between one-half and one with respect to water. The rate of the KF reaction was found to increase by nearly 5 orders of magnitude for a reagent in which the concentration of nonprotonated imidazole was increased from 0 (rate constant equal to 2.6 × 10(3) L(2) mol(-)(2) s(-)(1)) to about 7 mol/L. For most of these reagents, a recovery rate close to 100% was attained. A high concentration of nonprotonated imidazole in combination with a high concentration of sulfur dioxide could, however, lead to a change in stoichiometry of the KF reaction when larger amounts of water were determined (250 μg of water added to 3.4 mL of reagent solution). A reaction scheme is proposed which might explain this change in stoichiometry observed for some reagent compositions. By use of the described most rapidly reacting reagents, it was shown to be

  13. [Sweat chloride measurement using direct potentiometry: Spotchem(®) (Elitech-Arkray) evaluation and comparison with coulometry and conductivity].

    Science.gov (United States)

    Nguyen-Khoa, Thao; Borgard, Jean-Pierre; Miled, Ryad; Rota, Michèle

    2013-01-01

    Sweat chloride (Cl(-)) measurement is a key step for the diagnosis of cystic fibrosis. The coulometric technique is validated in this context by international guidelines. The aim of our study was to evaluate the assay for sweat Cl(-) ions using direct potentiometry on disposable cassette (Spotchem™ SE EL-1520, Elitech-Arkray) by comparing results to those obtained on the same sample, by coulometry (Chloride analyser Sherwood 926S, Dutscher). To complete our table of correspondence between the results of Cl(-) ions and sweat conductivity (Sweat Check™ 3100), conductivity has been also achieved for 99 of the 139 sweat samples studied. Linearity of each technique performed extends from 10 to 120 mmol/L. The coefficients of variation within and between runs are < 5%. Comparison of 139 results (Passing - Bablock regression) shows a significant difference (p < 0.001): [Spotchem] = 1.026 [Chloride analyser] + 1.8, r = 0.996. After correction with regression factors, only 6 pairs of values (4.6%) had a difference greater than ± 5 mmol/L). The results of conductivity measurement is strongly correlated with those of Cl(-) ions (r = 0.959 for Chloride analyser and 0.965 for Spotchem; p = 0.576) with a linear relationship between the decision thresholds from 30 to 60 mmol/L Cl(-). Sweat Cl(-) determinations using Spotchem™ analyser meet the criteria required by analytical recommendations. The technique is standardized, easy to perform and fast. Its good practicability makes the sweat test independent to operator and allows point-of care use.

  14. Colorimetry and constant-potential coulometry determinations of transferrin-bound iron, total iron-binding capacity, and total iron in serum containing iron-dextran, with use of sodium dithionite and alumina columns.

    Science.gov (United States)

    Jacobs, J C; Alexander, N M

    1990-10-01

    After the parenteral administration of iron-dextran (imferon), the increased total iron concentrations in serum can be determined by atomic absorption spectroscopy and by colorimetric methods involving sodium dithionite, which reductively dissociates iron from the dextran complex. We report that constant-potential coulometry detects only about 55-70% of dextran-bound iron before dithionite reduction and variable amounts after reaction with the reducing agent. In addition, we have developed a procedure for determining transferrin-bound iron, total iron-binding capacity (TIBC), total iron, and dextran-bound iron with the Kodak Ektachem colorimetric system. In determining total serum iron, the sample is first mixed with sodium dithionite, which rapidly dissociates all dextran-bound iron, but does not remove iron from either transferrin or hemoglobin. After the mixture is applied to an Ektachem slide, transferrin-bound iron is released at pH 4 and is detected together with the iron previously bound to dextran. TIBC is determined by mixing serum with ferric citrate in moderate excess and filtering through a small alumina (Al2O3) column, which binds excess free iron and iron-dextran; the iron in the column eluate represents the TIBC. Transferrin-bound iron is determined by applying diluted serum without added ferric citrate to an alumina column and measuring the iron in the column eluate. Dextran-bound iron is equivalent to the difference between total and transferrin-bound iron. Using this method, we found that transferrin iron-binding sites are saturated in vitro by excess iron-dextran less efficiently than by ferric citrate.

  15. 微库仑法测定柴油硫含量条件的优化探讨%Study on the conditions optimization of determination of the sulfur content in diesel oil by micro-coulometry

    Institute of Scientific and Technical Information of China (English)

    王义皓; 杨丽娜; 王长春; 王天星; 娄井阳

    2013-01-01

    The WK-2D microcoulometer was tuned.The injection volume,injection rate,gas flow rate,furnace temperature,four aspects which impact on the determination of sulfur content of the sample by micro-coulometry were discussed.and the appropriate formula and technologic condition were determined.Under optimization conditions,the precision and recovery rate of straight-run diesel spiked were studied.The results indicated:the injection volume was 1.3μL,injection speed of 38 scale.nitrogen flow 260 mL/min,the oxygen flow 150 mL/min,the vaporization segment temperature of 750 ℃,the combustion segment temperature of 850 ℃,the stable segment temperature of 650 ℃.The method of determination of sulfur content in straight-run diesel oil was reproducible,low error.The recovery was around 99 %~102 % and their RSD values were all lower than 1%.The method was simple,rapidness,accurate and fully suitable for large quantities of determination in the sulfur content of straightrun diesel oil.%对WK-2D型微库仑仪进行调试.从进样量、进样速度、气体流量、炉温4个方面讨论操作因素对微库伦法测定样品硫含量的影响,并确定最优操作条件.在优化条件下,对加标直馏柴油样品进行精密度和回收率考察.结果表明:进样量为1.3μL,进样速度为38档,氮气流量为260 mL/min,氧气流量为150 mL/min,汽化段温度为750℃,燃烧段温度为850℃,稳定段温度为650℃操作条件下测得直馏柴油硫含量误差低,重复性好.加标回收率在99%~102%,RSD<1%.该方法简单、快速、准确,适合大批量直馏柴油样品的测定.

  16. Coulometry for the detection of water content in archaeological findings

    Directory of Open Access Journals (Sweden)

    Vincenza Crupi

    2016-06-01

    Full Text Available In the present work, we performed coulometric measurements to detect the water content in archaeological pottery in order to get information on the manufacture technique. The samples under study were the so-called "Ionian Cups" coming from various archaeological sites in eastern Sicily (South-Italy. In particular, we tentatively achieved the estimation of firing temperatures of the archaeological samples by comparing the coulometric results with those obtained in the case of raw materials fired under controlled conditions. The results were in good agreement with those previously obtained on the same samples by Small Angle Neutron Scattering (SANS. It is worth underlying that for the first time, the detection of water content as revealed by this analytical technique was related to archaeometric issues.

  17. Ascorbic Acid Determination in Natural Orange Juice: As a Teaching Tool of Coulometry and Polarography.

    Science.gov (United States)

    Bertotti, Mauro; And Others

    1995-01-01

    Describes an experiment designed to determine ascorbic acid concentrations in natural orange juice. The experiment is used with undergraduate pharmacy students to allow understanding of the principles of operation of the coulometer and polarograph. (DDR)

  18. Voltammetry and Coulometry with Immersed Thin Layer Electrodes. Part 1. Model for Effects of Solution Resistivity in Linear Sweep Voltammetry.

    Science.gov (United States)

    1984-11-28

    and Sons, New York, 1980 2. A.J. Bard and K.S.V. Santhanam, in "A.J• Bard, ed., " Electroanalytical Chemistry ", vol. 4, Marcel Dekker, New "’’ York, 1970...A.T. Hubbard and F.C. Anson, Anal. Chem. 38, 58 (1966). 11. D.E. Smith in A.J. Bard, " Electroanalytical Chemistry " vol. 1, Marcel Dekker, New York

  19. Standard test method for determining plutonium by controlled-potential coulometry in H2SO4 at a platinum working electrode

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1990-01-01

    1.1 This test method covers the determination of milligram quantities of plutonium in unirradiated uranium-plutonium mixed oxide having a U/Pu ratio range of 0.1 to 10. This test method is also applicable to plutonium metal, plutonium oxide, uranium-plutonium mixed carbide, various plutonium compounds including fluoride and chloride salts, and plutonium solutions. 1.2 The recommended amount of plutonium for each aliquant in the coulometric analysis is 5 to 10 mg. Precision worsens for lower amounts of plutonium, and elapsed time of electrolysis becomes impractical for higher amounts of plutonium. 1.3 The values stated in SI units are to be regarded as standard. No other units are to be regarded as standard. 1.4 This standard does not purport to address all of the safety concens, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific precaution...

  20. Determination of micro content carbon element in catalytic cracking catalyst by coulometry%库仑法测定催化裂化催化剂中的微量碳

    Institute of Scientific and Technical Information of China (English)

    赵军; 张瑛; 陈亮; 马素娥; 乔涛

    2009-01-01

    An analytical method was developed for determination of micro content carbon in catalytic cracking catalyst by using automatic carbon and hydrogen element analyzer. The sample was conbusted in a high-temperature furnace, and the carbon element was changed into carbon dioxide, which was reacted with LiOH to produce water. The water produced was sent into an electrolytic cell. According to Faraday's law, the carbon content in the sample can be calculated with the quantity of electricity consumed in the electrolysis process. The method has the advantages of good repeatability, good precision, high accuracy, and low detection limit. It can be effectively used for catalyst analysis in production.%采用库仑法全自动碳氢元素分析仪,建立了一种催化裂化催化剂中微量碳含量的分析方法.样品经高温燃烧,碳生成二氧化碳,二氧化碳再与氢氧化锂反应生成相应的水,将水送入涂有五氧化二磷的电解池电解,测量电解所消耗的电量,依照法拉第电解定律计算出样品中的碳含量.实验证明,该分析方法重复性好,准确度高,检测限低,能够满足催化装置上的催化剂分析需要,对实际生产具有指导意义.

  1. An Electrochemical Experiment Using an Optically Transparent Thin Layer Electrode

    Science.gov (United States)

    DeAngelis, Thomas P.; Heineman, William R.

    1976-01-01

    Describes a unified experiment in which an optically transparent thin layer electrode is used to illustrate the techniques of thin layer electrochemistry, cyclic voltammetry, controlled potential coulometry, and spectroelectrochemistry. (MLH)

  2. The influence of the capping agent on the oxidation of silver nanoparticles: nano-impacts versus stripping voltammetry.

    Science.gov (United States)

    Toh, Her Shuang; Jurkschat, Kerstin; Compton, Richard G

    2015-02-09

    The influence of capping agents on the oxidation of silver nanoparticles was studied by using the electrochemical techniques of anodic stripping voltammetry and anodic particle coulometry ("nano-impacts"). Five spherical silver nanoparticles each with a different capping agent (branched polyethylenimine (BPEI), citrate, lipoic acid, polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP)) were used to perform comparative experiments. In all cases, regardless of the capping agent, complete oxidation of the single nanoparticles was seen in anodic particle coulometry. The successful quantitative detection of the silver nanoparticle size displays the potential application of anodic particle coulometry for nanoparticle characterisation. In contrast, for anodic stripping voltammetry using nanoparticles drop casting, it was observed that the capping agent has a very significant effect on the extent of silver oxidation. All five samples gave a low oxidative charge corresponding to partial oxidation. It is concluded that the use of anodic stripping voltammetry to quantify nanoparticles is unreliable, and this is attributed to nanoparticle aggregation.

  3. The reduction mechanism at the mercury electrode in a 0.9 M NaClO4+0.1 M HClO4 supporting electrolyte of an hydroxytriphenylmethane: Eriochrome Cyanine R

    NARCIS (Netherlands)

    Boodts, J.F.C.; Sluyters-Rehbach, M.; Sluyters, J.H.

    1979-01-01

    The reduction mechanism at a mercury electrode of Eriochrome Cyanine R, in a 0.9 M NaClO4+0.1 M HClO4 supporting electrolyte, has been investigated by several electrochemical techniques. By means of coulometry at constant potential and cyclic voltammetry it was demonstrated that a radical is formed,

  4. Nanoparticle-electrode collision processes: the underpotential deposition of thallium on silver nanoparticles in aqueous solution.

    Science.gov (United States)

    Zhou, Yi-Ge; Rees, Neil V; Compton, Richard G

    2011-08-01

    The electrochemistry of collisions between metal nanoparticles (NPs) and electrode surfaces has been of recent interest with the development of anodic particle coulometry as a characterisation method. For the first time the underpotential deposition of metal ions from solution onto metal nanoparticles during collisions between the NPs and an inert electrode is reported.

  5. Electrochemical properties of pyridine and dihydropyridine derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Abou-Elenien, G.; Rieser, J.; Ismail, N.; Wallenfels, K.

    1981-03-01

    The electrochemical oxidation and reduction properties of different dihydropyridines and pyridines have been investigated in non aqueous solvent as benzonitrile and acetonitrile with tetra-n-butylammonium perchlorate as supporting electrolyte at platinum electrodes using DC-voltametry, cycl. voltametry and coulometry. Possible redox-mechanisms are discussed.

  6. Modern Chemical Technology, Volume 9.

    Science.gov (United States)

    Pecsok, Robert L.; Chapman, Kenneth

    This volume is one of the series for the Chemical Technician Curriculum Project (ChemTeC) of the American Chemical Society funded by the National Science Foundation. It consists of discussions, exercises, and experiments on the following topics: ion exchange, electrphoresis, dialysis, electrochemistry, corrosion, electrolytic cells, coulometry,…

  7. Mechanistic study of electrochemical oxidation of catechols in the presence of 4-hydroxy-1-methyl-2(1H)-quinolone

    Energy Technology Data Exchange (ETDEWEB)

    Fakhari, Ali Reza [Department of Chemistry, Faculty of Science, University of Shahid Beheshti, Tehran 19835389 (Iran, Islamic Republic of)]. E-mail: a-zavareh@sbu.ac.ir; Nematollahi, Davood [Department of Chemistry, Faculty of Science, University of Bu-Ali-Sina, Hamadan (Iran, Islamic Republic of); Moghaddam, Abdolmajid Bayandori [Department of Chemistry, Faculty of Science, University of Shahid Beheshti, Tehran 19835389 (Iran, Islamic Republic of)

    2005-09-20

    Electrochemical oxidation of catechols (1a-1c) has been studied in the presence of 4-hydroxy-1-methyl-2(1H)-quinolone (3) as a nucleophile in aqueous solution using cyclic voltammetry and controlled-potential coulometry. The results indicate that the quinones derived from catechols (1a-1c) participate in Michael addition reactions with 3 to form the corresponding benzofuran (or isochromeno[4,3-c]quinoline) derivatives (6a-6c). The electrochemical synthesis of (6a-6c) has been successfully performed in an undivided cell in good yield and purity. The oxidation mechanism was deduced from voltammetric data and by coulometry at controlled-potential. The products have been characterized after purification by IR, {sup 1}H NMR, {sup 13}C NMR and MS.

  8. Standard test methods for chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade boron carbide

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2004-01-01

    1.1 These test methods cover procedures for the chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade boron carbide powder and pellets to determine compliance with specifications. 1.2 The analytical procedures appear in the following order: Sections Total Carbon by Combustion and Gravimetry 7-17 Total Boron by Titrimetry 18-28 Isotopic Composition by Mass Spectrometry 29-38 Chloride and Fluoride Separation by Pyrohydrolysis 39-45 Chloride by Constant-Current Coulometry 46-54 Fluoride by Ion-Selective Electrode 55-63 Water by Constant-Voltage Coulometry 64-72 Impurities by Spectrochemical Analysis 73-81 Soluble Boron by Titrimetry 82-95 Soluble Carbon by a Manometric Measurement 96-105 Metallic Impurities by a Direct Reader Spectrometric Method 106-114

  9. First mercury reference laboratory is established in Southern Africa

    CSIR Research Space (South Africa)

    Somerset, VS

    2010-01-01

    Full Text Available of Chemistry?Environmental Chemistry Group?Bulletin?January 2010 22 Monitoring trace metals in the envi- ronment Heavy metals are some of the most widespread of environ- mental pollutants. They originate predominantly from an- thropogenic activities...(3), 155-159. Beinrohr, E.; Cakrt, M.; Dzurov, J.; Kottas, P.; Kozakova, E. (1996). Calibrationless determination of mercury by flow- through stripping coulometry. Fresenius? Journal of Analyti- cal Chemistry, 365(3-4), 253-258. Royal Society...

  10. Diversity in electrochemical oxidation of dihydroxybenzenes in the presence of 1-methylindole

    Indian Academy of Sciences (India)

    Davood Nematollahi; Vahid Hedayatfar

    2011-09-01

    Electrochemical oxidation of some catechol derivatives (1a-e) have been studied in water/acetonitrile solution containing 1-methylindole (3) as a nucleophile, using cyclic voltammetry and controlledpotential coulometry. An interesting diversity in the mechanisms has been observed in electrochemical oxidation of catechol derivatives (1a-e) in the presence of 3. In this work, we have proposed reaction schemes , and for oxidation of 1a-e in the presence of 3.

  11. Organic Electrochemistry in Aluminum Chloride Melts.

    Science.gov (United States)

    1976-08-15

    Cyclic voltametry revealed adamantane and l-methyladamanta1ie to be electroactive at a tungsten electrode * well within the background limits of molten...diphenylmethane. Coulometry cyclic voltametry and ring-disc electrode studies were carried out to elucidate a mechanism for the reaction. It was shown that...the viscosity was found to be 25 cp and the • I conductivity, 3 x 1O~ ohm~ cm ’. A variety of electrode materials were surveyed via cyclic voltaninetry

  12. Electrochemical Synthesis and Kinetic Evaluation of Electrooxidation of Acetaminophen in the Presence of Antidepressant Drugs

    OpenAIRE

    Nematollahi, Davood; Feyzi Barnaji, Bahareh; Amani, Ameneh

    2015-01-01

    With the aim of obtaining information about drug-drug interaction (DDI) between acetaminophen and some of antidepressant drugs (fluoxetine, sertraline and nortriptyline), in the present work we studied the electrochemical oxidation of acetaminophen (paracetamol) in the presence of these drugs by means of cyclic voltammetry and Controlled-potential coulometry. The reaction between N-acetyl-p-benzoquinone-imine (NAPQI) produced from electrooxidation of acetaminophen and antidepressant drugs (se...

  13. Partitioning of metals in different binding phases of tropical estuarine sediments: importance of metal chemistry

    Digital Repository Service at National Institute of Oceanography (India)

    Chakraborty, P.; Chakraborty, S.; Vudamala, K.; Sarkar, Arindam; Nath, B.N.

    analyzed for total carbon (TC), total inorganic carbon (TIC), total nitrogen (TN) content. TC and TN in sediments were determined by using Flash 2000 CHN- elemental analyzer (Thermo Fisher Scientific Incorporation). Precision of the analysis was within... ± 5%. Soil NC was used as certified reference material. TIC was determined by coulometry (UIC coulometrics). Total organic carbon (TOC) was derived by subtracting TIC from TC. Sequential extraction method for metal speciation The sequential...

  14. Electrochemical determination of water in environmental hydraulic fluids using the karl Fischer reaction.

    Science.gov (United States)

    Cedergren, A; Lundström, M

    1997-10-01

    Different procedures based on the Karl Fischer reaction were investigated with respect to their applicability for water determinations in environmental hydraulic fluids:  (i) continuous coulometry using a recently described diaphragm-free cell; (ii) on-line stripping of water at elevated temperature using either continuous coulometry or direct potentiometry for detection of the liberated water. Except for one of the oils, Statoil PA, which is a poly(α-olefin) with certain polymers added, no significant difference was found among coulometry using an optimized imidazole-buffered methanolic reagent containing 75% (v/v) chloroform, the two different stripping techniques (working in the temperature interval 100-110 °C), and the commercially available Hydranal Coulomat AG-H. The high stability and sensitivity of the coulometric technique described made it possible to work with sample amounts in the low milligram-range, and this is shown to increase the reliability of the coulometric method as compared to normally used procedures.

  15. Determination of Chlorine Dioxide and Chlorite in Water Supply Systems by Verified Methods

    Science.gov (United States)

    Tkáčová, Jana; Božíková, Jarmila

    2014-07-01

    This work is dedicated to the development and optimization of appropriate analytical methods for the determination of chlorine dioxide and chlorite in drinking water in order to obtain accurate and correct results in the quality control of drinking water. The work deals with the development and optimization of a method for the determination of chlorine dioxide using chlorophenol red. Furthermore, a new spectrophotometric method for the determination of chlorite via bromometry using methyl orange was developed, optimized and validated. An electrochemical method for the determination of chlorite by flow coulometry was also developed, optimized and validated.

  16. Applications of electrochemical techniques in mineral analysis.

    Science.gov (United States)

    Niu, Yusheng; Sun, Fengyue; Xu, Yuanhong; Cong, Zhichao; Wang, Erkang

    2014-09-01

    This review, covering reports published in recent decade from 2004 to 2013, shows how electrochemical (EC) techniques such as voltammetry, electrochemical impedance spectroscopy, potentiometry, coulometry, etc., have made significant contributions in the analysis of minerals such as clay, sulfide, oxide, and oxysalt. It was discussed based on the classifications of both the types of the used EC techniques and kinds of the analyzed minerals. Furthermore, minerals as electrode modification materials for EC analysis have also been summarized. Accordingly, research vacancies and future development trends in these areas are discussed.

  17. Reduction of CO2 by nickel (II) macrocycle catalyst at HMDE

    Indian Academy of Sciences (India)

    M Aulice Scibioh; P V Ragini; S Rani; V R Vijayaraghavan; B Viswanathan

    2001-08-01

    With the aim of finding a suitable electrocatalyst for the efficient reduction of carbon dioxide, the electrochemistry of nickel (II) complex of 1,3,6,9,11,14-hexaazatricyclo [12 2 1 1] octadecane was studied using cyclic voltammetry (CV) and controlled-potential electrolysis (CPE) techniques in the presence and absence of CO2 in 100% H2O, CH3CN-H2O mixtures (20-100%) and DMF-H2O (70-100%) mixtures. The efficiency of this process is determined using the coulometry technique. CO is the major product in the gaseous phase and HCOOH the sole product formed in the solution phase.

  18. Determination of Chlorine Dioxide and Chlorite in Water Supply Systems by Verified Methods

    Directory of Open Access Journals (Sweden)

    Tkáčová Jana

    2014-07-01

    Full Text Available This work is dedicated to the development and optimization of appropriate analytical methods for the determination of chlorine dioxide and chlorite in drinking water in order to obtain accurate and correct results in the quality control of drinking water. The work deals with the development and optimization of a method for the determination of chlorine dioxide using chlorophenol red. Furthermore, a new spectrophotometric method for the determination of chlorite via bromometry using methyl orange was developed, optimized and validated. An electrochemical method for the determination of chlorite by flow coulometry was also developed, optimized and validated.

  19. Determination of water in NIST reference material for mineral oils

    Science.gov (United States)

    Cedergren; Nordmark

    2000-07-15

    The accuracy of the reference concentrations of moisture in electrical insulating oil RM 8506 and lubricating oil RM 8507 (both of mineral type) and specified by the National Institute of Standards and Technology (NIST) as containing 39.7 and 76.8 ppm (w/w) water, respectively, has recently been the subject of debate in this journal. To shed some further light on this controversy, we report in this correspondence results for these oils obtained by two additional methods, one based on specially designed reagents for diaphragm-free Karl Fischer (KF) coulometry and the other based on the concept of stripping at elevated temperature/continuous KF coulometry. A positive interference effect was shown to take place for RM 8506 when the direct coulometric method was used. If the results are corrected for this, the values including six different procedures varied in the range 13.5-15.6 ppm (w/w). For RM 8507, all values were between 42.5 and 47.2 ppm (w/w), which means that the values recommended by NIST for both reference oils using volumetric titration are about twice as high as those obtained with the other techniques. A possible explanation for this discrepancy is presented.

  20. Direct Measurement of Electron Transfer in Nanoscale Host-Guest Systems: Metallocenes in Carbon Nanotubes.

    Science.gov (United States)

    McSweeney, Robert L; Chamberlain, Thomas W; Baldoni, Matteo; Lebedeva, Maria A; Davies, E Stephen; Besley, Elena; Khlobystov, Andrei N

    2016-09-12

    Electron-transfer processes play a significant role in host-guest interactions and determine physicochemical phenomena emerging at the nanoscale that can be harnessed in electronic or optical devices, as well as biochemical and catalytic systems. A novel method for qualifying and quantifying the electronic doping of single walled carbon nanotubes (SWNTs) using electrochemistry has been developed that establishes a direct link between these experimental measurements and ab initio DFT calculations. Metallocenes such as cobaltocene and methylated ferrocene derivatives were encapsulated inside SWNTs (1.4 nm diameter) and cyclic voltammetry (CV) was performed on the resultant host-guest systems. The electron transfer between the guest molecules and the host SWNTs is measured as a function of shift in the redox potential (E1/2 ) of Co(II) /Co(I) , Co(III) /Co(II) and Fe(III) /Fe(II) . Furthermore, the shift in E1/2 is inversely proportional to the nanotube diameter. To quantify the amount of electron transfer from the guest molecules to the SWNTs, a novel method using coulometry was developed, allowing the mapping of the density of states and the Fermi level of the SWNTs. Correlated with theoretical calculations, coulometry provides an accurate indication of n/p-doping of the SWNTs.

  1. PILOT STUDY: CCQM-P32 pilot study. Anion calibration solutions

    Science.gov (United States)

    Weber, Michael; Wüthrich, Jürg

    2003-01-01

    In the CCQM-P32 pilot study two gravimetrically prepared anion calibration solutions of chloride and phosphate each of about 1 g/kg mass fraction were investigated. The comparison was an activity of the Inorganic Analysis Working Group of CCQM in 2002 and was piloted by the Swiss Federal Laboratories for Materials Testing and Research (EMPA). The following institutes participated in this study (in alphabetical order): BAM (Germany), CENAM (Mexico), EMPA (Switzerland), GUM (Poland), KRISS (South Korea), LNE (France), NIST (United States of America), NMIJ (Japan), NRCCRM (China), PTB (Germany), SMU (Slovakia). For the chloride calibration solution 11 participants provided 16 results by the following analytical techniques: coulometry (7), titrimetry (5) and ion chromatography (4). The phosphate amount content was determined by 9 NMIs and 11 results were reported. Phosphate ion chromatography was the most applied technique (4), followed by titrimetry (2), ICP-OES (2), gravimetry (1) and ion-exchange coulometry (1). All results were found within a range of +/-0.5% with respect to the gravimetric value. The variability (RSD) of the results is 0.13% for chloride and 0.26% for phosphate. The reported results of all participants are also graphically displayed in this report. Main text. To reach the main text of this paper, click on Final Report. The final report has been peer-reviewed and approved for publication by the CCQM Working Group on Inorganic Analysis, according to the provisions of the Mutual Recognition Arrangement (MRA).

  2. Coulometric generation of reagents using permselective interphases. Pt. 3. Pulse coulometric determination of sulphate in water and oil samples; precipitation titration as PbSO/sub 4/ in mixed solvents

    Energy Technology Data Exchange (ETDEWEB)

    Schumacher, E.; Hackmann, B.

    1981-01-01

    A method for precipitation-titrimetric determination of sulphate by coulometrically generated Pb/sup 2 +/ is described. The Pb/sup 2 +/ ions are transported by an equivalent current across a n-PbSe-membrane. Coulometry is performed with a specially developed pulse-coulometer which generates defined pulses with variable delay time. Adsorption effects on differently pretreated Pt-electrodes are used for indication. Precipitation is performed in wateracetone mixtures, acidified by addition of perchloric acid. The method has been tested on rain-water samples, tap-water samples, mineral waters and (after combustion) on oil samples. Comparison with alternative methods proves the more precise and correct results of our new method, combined with better possibilities for automation.

  3. The development of a micropatterned electrode for studies of zinc electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Sutija, Dave P. [Univ. of California, Berkeley, CA (United States); Muller, Rolf H. [Univ. of California, Berkeley, CA (United States); Tobias, Charles W. [Univ. of California, Berkeley, CA (United States)

    1986-12-01

    A micropatterned electrode was prepared for the study of electrocrystallization. Using microphotolithography, in conjunction with evaporation and pulse electrodeposition of thin films, a set of artificially roughened electrodes with hemispherical surface features five microns in diameter was developed. Voltammetric studies were conducted to determine the best electrode material. Gold, platinum, and various carbon surfaces were evaluated for zinc nucleation density and hydrogen overpotential. Surface homogeneity was examined by both light and scanning electron microscopy. Gold was determined to possess the best combination of material properties: chemical inertness, low melting point, and a high work function allowing underpotential deposition of zinc which reduces the rate of hydrogen evolution. Stripping coulometry was employed to determine zinc limiting currents, and evaluate effective diffusion coefficients in concentrated zinc chloride solutions. Although the method worked well for dilute zinc chloride and copper sulfate solutions, it failed at higher current densities; the emergence of surface roughness obscured actual limiting current plateaus.

  4. Cobalt, titanium or cerium oxide protective coatings for the nickel cathode of the molten carbonate fuel cells; Revetements protecteurs a base d'oxyde de cobalt, de titane ou de cerium pour la cathode de nickel des piles a combustible a carbonates fondus

    Energy Technology Data Exchange (ETDEWEB)

    Mendoza Blanco, L.

    2003-10-15

    The aim of this work is to combine the MCFC cathode Li{sub x}Ni{sub 1-x}O properties to those of the protective coatings of LiCoO{sub 2}, Li{sub 2}TiO{sub 3} or of CeO{sub 2}, less soluble in the molten carbonates. In the cases of LiCoO{sub 2}, have been carried out by controlled potential coulometry in aqueous solution, a deposition of Co{sub 3}O{sub 4} on dense Ni. The cobalt oxide reacts rapidly in the Li{sub 2}CO{sub 3}-Na{sub 2}CO{sub 3} medium at 650 C to give LiCoO{sub 2}, a spinel cubic phase revealed by Raman spectroscopy. (O.M.)

  5. Standard test methods for chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade plutonium dioxide powders and pellets

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 These test methods cover procedures for the chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade plutonium dioxide powders and pellets to determine compliance with specifications. 1.2 The analytical procedures appear in the following order: Sections Plutonium Sample Handling 8 to 10 Plutonium by Controlled-Potential Coulometry Plutonium by Ceric Sulfate Titration Plutonium by Amperometric Titration with Iron(II) Plutonium by Diode Array Spectrophotometry Nitrogen by Distillation Spectrophotometry Using Nessler Reagent 11 to 18 Carbon (Total) by Direct Combustion–Thermal Conductivity 19 to 30 Total Chlorine and Fluorine by Pyrohydrolysis 31 to 38 Sulfur by Distillation Spectrophotometry 39 to 47 Plutonium Isotopic Analysis by Mass Spectrometry Rare Earth Elements by Spectroscopy 48 to 55 Trace Elements by Carrier–Distillation Spectroscopy 56 to 63 Impurities by ICP-AES Impurity Elements by Spark-Source Mass Spectrography 64 to 70 Moisture by the Coulomet...

  6. Standard test methods for chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade mixed oxides ((U, Pu)O2)

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 These test methods cover procedures for the chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade mixed oxides, (U, Pu)O2, powders and pellets to determine compliance with specifications. 1.2 The analytical procedures appear in the following order: Sections Uranium in the Presence of Pu by Potentiometric Titration Plutonium by Controlled-Potential Coulometry Plutonium by Amperometric Titration with Iron (II) Nitrogen by Distillation Spectrophotometry Using Nessler Reagent 7 to 14 Carbon (Total) by Direct Combustion-Thermal Conductivity 15 to 26 Total Chlorine and Fluorine by Pyrohydrolysis 27 to 34 Sulfur by Distillation-Spectrophotometry 35 to 43 Moisture by the Coulometric, Electrolytic Moisture Analyzer 44 to 51 Isotopic Composition by Mass Spectrometry Rare Earths by Copper Spark Spectroscopy 52 to 59 Trace Impurities by Carrier Distillation Spectroscopy 60 to 69 Impurities by Spark-Source Mass Spectrography 70 to 76 Total Gas in Reactor-Grade Mixed Dioxide P...

  7. Corrosion protection of copper by a self-assembled monolayer of alkanethiol

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Y.; Teo, W.K.; Siow, K.S.; Gao, Z.; Tan, K.L.; Hsieh, A.K. [National Univ. of Singapore (Singapore)

    1997-01-01

    A self-assembled monolayer of 1-dodecanethiol (DT) was formed on a copper surface pretreated using different methods. The corrosion protection abilities of the monolayer were evaluated in an air-saturated 0.51 M NaCl solution using various techniques including electrochemical impedance spectroscopy, polarization, coulometry, weight loss, and X-ray photoelectron spectroscopy. It was found that the corrosion resistance of the monolayer was improved markedly by using a nitric acid etching method. A minimum concentration of 10{sup {minus}4} M DT was needed to form a protective monolayer. The DT-monolayer retarded the reduction of dissolved oxygen and inhibited the growth of copper oxide in the NaCl solution. In comparison with other inhibitors, such as benzotriazole (BTA) and mercapto-benzothiazole (MBT), the DT-monolayer showed much better corrosion resistance in aqueous solution.

  8. Electrochemical reduction of chloridazon at mercury electrodes, and its analytical application.

    Science.gov (United States)

    Zimpl, M; Kotoucek, M; Lemr, K; Veselá, J; Skopalová, J

    2001-12-01

    The electrochemical behavior of the herbicide chloridazon, I (pyrazon), at different pH is described. The electrode reaction (one wave in acidic media and another in alkaline media), investigated using direct current and pulse voltammetry, controlled-potential coulometry, and HPLC-MS, is a combination of the electroreduction (two-electron in the first step) and a kinetic process as a result of which simple compounds (HCl, NH3) are released and, moreover, a five-membered pyrrole cycle is formed in strongly acid media. Products of the kinetic reaction are further reducible. The dissociation constant of I, pKa = 2.96, was found spectrophotometrically. Fast-scan differential pulse voltammetry (FSDPV) was used for determination of I; the detection limit was 2.7 x 10(-8) mol L(-1) (0.006 microg L(-1)) at pH 2.3. Chloridazon was determined in spiked drinking and river water.

  9. [Simultaneous determination of trace amounts of zinc, cadmium, lead and copper by the method of anodic voltammetry using factor experimental design].

    Science.gov (United States)

    Koen, E

    1975-01-01

    Using the method of factor planning of the experiment, the author studies and demonstrates the influence exerted by the potential and time of electrolysis, and by the concentration of the background and elements on the heights of anodal peaks upon simultaneous determination of zinc, cadmium, lead and copper microconcentrations. On the ground of statistical elaboration of the results, the optimal condition for polarographic determination through anodal voltamperometry are outlined. According to the cyclic voltametry method, the electrod processes reversibility for zinc, cadmium and lead, as well as the incomplete reversibility for copper are established; the number of electrons participating in the electrochemical reaction are found using the method of gas coulometry. The possibility of simultaneous determination of the four elements' ultramicroconcentrations after the method of voltamperometry with enrichment is proved. The standard deviation is in the range 3.02 to 4.9.

  10. A study on the electrodeposition of NiFe alloy thin films using chronocoulometry and electrochemical quartz crystal microgravimetry

    CERN Document Server

    Myung, N S

    2001-01-01

    Ni, Fe and NiFe alloy thin films were electrodeposited at a polycrystalline Au surface using a range of electrolytes and potentials. Coulometry and EQCM were used for real-time monitoring of electroplating efficiency of the Ni and Fe. The plating efficiency of NiFe alloy thin films was computed with the aid of ICP spectrometry. In general, plating efficiency increased to a steady value with deposition time. Plating efficiency of Fe was lower than that of Ni at -0.85 and -1.0 V but the efficiency approached to the similar plateau value to that of Ni at more negative potentials. The films with higher content of Fe showed different stripping behavior from the ones with higher content of Ni. Finally, compositional data and real-time plating efficiency are presented for films electrodeposited using a range of electrolytes and potentials.

  11. Electrochemistry of hexanitroazobenzene: reactivity with metals and synthetic implications

    Energy Technology Data Exchange (ETDEWEB)

    Firsich, D.W.

    1985-08-08

    The electrochemical properties of hexanitroazobenzene (HNAB) are defined as an aid towards understanding the general reactivity of this commonly used explosive. Cyclic voltammetry, controlled potential coulometry, and visible spectroscopy are used to characterize the anion, dianion, protonated dianion, and diprotonated dianion of HNAB. The acid/base relationships of these species are established, and their role in the present synthetic method for producing HNAB is clearly defined. The feasibility of an electrochemical synthesis for HNAB is demonstrated. It is shown that the reaction between aluminum metal and HNAB in solution produces the protonated dianion of HNAB, and that reactions between other common metals and HNAB do occur. The visible absorption maxima of a number of possible decomposition products of HNAB are compiled. Related chemistry involving a triazole oxide derivative is presented. 5 refs., 5 figs., 2 tabs.

  12. Mechanistic study of electrochemical oxidation of o-dihydroxybenzenes in the presence of 4-hydroxy-1-methyl-2(1H)-quinolone

    Energy Technology Data Exchange (ETDEWEB)

    Moghaddam, Abdolmajid Bayandori [Department of Medicinal Chemistry, School of Pharmacy, Shahid Beheshti University of Medical Sciences, Tehran 1983963113 (Iran, Islamic Republic of)]. E-mail: bayandori@gmail.com; Kobarfard, Farzad [Department of Medicinal Chemistry, School of Pharmacy, Shahid Beheshti University of Medical Sciences, Tehran 1983963113 (Iran, Islamic Republic of); Fakhari, Ali Reza [Department of Chemistry, Faculty of Science, University of Shahid Beheshti, Tehran (Iran, Islamic Republic of); Nematollahi, Davood [Department of Chemistry, Faculty of Science, University of Bu-Ali-Sina, Hamadan (Iran, Islamic Republic of); Davarani, Saied Saeed Hosseiny [Department of Chemistry, Faculty of Science, University of Shahid Beheshti, Tehran (Iran, Islamic Republic of)

    2005-11-01

    Electrochemical oxidation of o-dihydroxybenzenes (1a and 1b) has been studied in the presence of 4-hydroxy-1-methyl-2(1H)-quinolone (3) as a nucleophile in aqueous solution using cyclic voltammetry and controlled-potential coulometry. The results indicate that the o-quinones derived from o-dihydroxybenzenes (1a and 1b) participate in 1,4-(michael) addition reactions with 3 to form the corresponding new o-dihydroxybenzene derivatives (6a and 6b). We propose a mechanism for the electrode process. The efficient electrochemical synthesis of 6a and 6b has been successfully performed at carbon rod electrodes in an undivided cell in good yield and purity. The products have been characterized after purification by IR, {sup 1}H NMR, {sup 13}C NMR and MS.

  13. Electroanalytical studies of sulfentrazone in protic medium, its degradation by the electro-Fenton process, and toxicity assessment using ss-DNA.

    Science.gov (United States)

    de A Lima, Augusto C; dos S Melo, Acácia M; Pires, Edjane Vieira; dos Santos Ferreira, Roberta Costa; Sant'Ana, Antônio E G; Goulart, Marília O F; de Abreu, Fabiane C

    2010-11-01

    Sulfentrazone is an herbicide used as a pre-plant incorporated or pre-emergence treatment. The electrochemical oxidation of sulfentrazone was studied, by cyclic, differential and square-wave voltammetry on unmodified and on glassy carbon nanotube-modified electrodes, and by controlled-potential coulometry and electrolysis. The voltammograms of sulfentrazone showed a main irreversible diffusion-controlled pH-dependent oxidation peak. The in situ DNA-damaging capacity of sulfentrazone was also investigated, employing double stranded ds-DNA-modified glassy carbon electrode, without evidence of interaction. On the other hand, in a solution of sulfentrazone and single stranded ss-DNA, the oxidation signals of the respective bases decreased concentration-dependently, indicating binding of sulfentrazone to guanine and adenine. The electro-Fenton method was employed to promote decontamination by eliminating the herbicide, resulting in almost 60% of mineralization.

  14. Clean and Green Synthesis of New Benzothiazole Derivatives via Electrochemical Oxidation of Catechol Derivatives

    Directory of Open Access Journals (Sweden)

    Mansour Arab Chamjangali

    2016-06-01

    Full Text Available Electrochemical oxidation of the catechols 1a and 1b is studied in the presence of 6-methyl-2-thouracil (3b and 6-propyl-2-thiouracil (3a as nucleophiles in a phosphate buffer (0.15 mol L−1, pH = 6.8/DMF (95:5 solution using cyclic voltammetry and controlled-potential coulometry. The results obtained indicate that the quinones derived from the catechols participate in 1,4-Michael-addition reactions with the nucleophiles to form the corresponding new benzothiazole compounds. In this work, we derive a variety of products with good yields using controlled potential at graphite electrodes in an undivided cell. This work is licensed under a Creative Commons Attribution 4.0 International License.

  15. Electrochemical hydrogenation of thiophene on SPE electrodes

    Science.gov (United States)

    Huang, Haiyan; Yuan, Penghui; Yu, Ying; Chung, Keng H.

    2017-01-01

    Electrochemical reduction desulfurization is a promising technology for petroleum refining which is environmental friendly, low cost and able to achieve a high degree of automation. Electrochemical hydrogenation of thiophene was performed in a three-electrode system which SPE electrode was the working electrode. The electrochemical desulfurization was studied by cyclic voltammetry and bulk electrolysis with coulometry (BEC) techniques. The results of cyclic voltammetry showed that the electrochemical hydrogenation reduction reaction occurred at -0.4V. The BEC results showed that the currents generated from thiophene hydrogenation reactions increased with temperature. According to Arrhenius equation, activation energy of thiophene electrolysis was calculated and lower activation energy value indicated it was diffusion controlled reaction. From the products of electrolytic reactions, the mechanisms of electrochemical hydrogenation of thiophene were proposed, consisting of two pathways: openingring followed by hydrogenation, and hydrogenation followed by ring opening.

  16. A promising green method in cyclization reaction.Oxidation of 3-methylcatechol in the presence of 1,10-phenanthroline

    Institute of Scientific and Technical Information of China (English)

    Davood Nematollahi; Bita Dadpou

    2011-01-01

    Electrochemical oxidation of 3-methylcatechol as a model compound has been studied in the presence of 1,10-phenanthroline as a bi-dentate nucleophile in water/acetonitrile (70/30, v/v) solution using cyclic voltammetry and controlled-potential coulometry. The results revealed that anodically generated 3-methylcyclohexa-3,5-diene-l,2-dione participates in inter and intramolecular Michael addition reactions with 1,10-phenanthroline and via an ECEC pathway converts to the corresponding heterocyclic compound. The present work has led to the development of a facile and one-pot method with high atom economy under ambient conditions and in an undivided cell using a carbon electrode.

  17. Electrochemical Reduction of 1,2-Di(p-tolylimino)ethane and 1,2-Di(2,4-dimethylphenylimino)ethane in Dimethylformamide

    Institute of Scientific and Technical Information of China (English)

    FOTOUHI, Lida; ZEIENALI, Mahbobeh; DEHGHANPOUR, Saeed; NEMATOLLAHI, Davood

    2007-01-01

    1,2-Di(p-tolylimino)ethane (Ⅰ) and 1,2-Di(2,4-dimethylphenylimino)ethane (Ⅱ) were synthesized and their electrochemical behavior investigated in dimethylformamide using classical voltammetry, differential pulse voltammetry, cyclic voltammetry, chronoamperometry, controlled potential electrolysis and coulometry. Both bis-Schiff base ligands examined show a cathodic irreversible peak which corresponds to one-electron reduction of the substrate to form anion radical. According to the fact obtained from cyclic voltammetry, that the current function(ip/v1/2) is a decreasing function of the scan rate, it can be concluded that there is a following coupling chemical reaction (EC mechanism). Thus, the most probable mechanism of electroreduction of both ligands is the coupling of two radicals to form a dimer.

  18. Standard test methods for chemical, mass spectrometric, spectrochemical, nuclear, and radiochemical analysis of nuclear-grade plutonium nitrate solutions

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 These test methods cover procedures for the chemical, mass spectrometric, spectrochemical, nuclear, and radiochemical analysis of nuclear-grade plutonium nitrate solutions to determine compliance with specifications. 1.2 The analytical procedures appear in the following order: Sections Plutonium by Controlled-Potential Coulometry Plutonium by Amperometric Titration with Iron(II) Plutonium by Diode Array Spectrophotometry Free Acid by Titration in an Oxalate Solution 8 to 15 Free Acid by Iodate Precipitation-Potentiometric Titration Test Method 16 to 22 Uranium by Arsenazo I Spectrophotometric Test Method 23 to 33 Thorium by Thorin Spectrophotometric Test Method 34 to 42 Iron by 1,10-Phenanthroline Spectrophotometric Test Method 43 to 50 Impurities by ICP-AES Chloride by Thiocyanate Spectrophotometric Test Method 51 to 58 Fluoride by Distillation-Spectrophotometric Test Method 59 to 66 Sulfate by Barium Sulfate Turbidimetric Test Method 67 to 74 Isotopic Composition by Mass Spectrom...

  19. Beyond potentiometry: robust electrochemical ion sensor concepts in view of remote chemical sensing.

    Science.gov (United States)

    Bakker, Eric; Bhakthavatsalam, Vishnupriya; Gemene, Kebede L

    2008-05-15

    For about 100 years, potentiometry with ion-selective electrodes has been one of the dominating electroanalytical techniques. While great advances in terms of selective chemistries and materials have been achieved in recent years, the basic manner in which ion-selective membranes are used has not fundamentally changed. The potential readings are directly co-dependent on the potential at the reference electrode, which requires maintenance and for which very few accepted alternatives have been proposed. Fouling or clogging of the exposed electrode surfaces will lead to changes in the observed potential. At the same time, the Nernst equation predicts quite small potential changes, on the order of millivolts for concentration changes on the order of a factor two, making frequent recalibration, accurate temperature control and electrode maintenance key requirements of routine analytical measurements. While the relatively advanced selective materials developed for ion-selective sensors would be highly attractive for low power remote sensing application, one should consider solutions beyond classical potentiometry to make this technology practically feasible. This paper evaluates some recent examples that may be attractive solutions to the stated problems that face potentiometric measurements. These include high-amplitude sensing approaches, with sensitivities that are an order of magnitude larger than predicted by the Nernst equation; backside calibration potentiometry, where knowledge of the magnitude of the potential is irrelevant and the system is evaluated from the backside of the membrane; controlled current coulometry with ion-selective membranes, an attractive technique for calibration-free reagent delivery without the need for standards or volumetry; localized electrochemical titrations at ion-selective membranes, making it possible to design sensors that directly monitor parameters such as total acidity for which volumetric techniques were traditionally used

  20. Rock magnetic and other geophysical signatures of relative sea level change in the Middle Cambrian Wheeler Formation, Drum Mountains, West-Central Utah

    Science.gov (United States)

    Halgedahl, S. L.; Jarrard, R. D.

    2011-12-01

    The Wheeler Formation of West-Central Utah is a succession of mixed carbonate-siliciclastic rocks deposited during the Middle Cambrian along a passive continental margin of Laurentia (western margin, in today's coordinates). The depositional setting was a gentle ramp, bounded by a normal fault on the south. The present study focuses on the Wheeler Formation in the Drum Mountains, Utah, which is thought to have recorded Middle Cambrian sea level changes and which is known to yield exceptionally-preserved fossils with soft parts, similar to the famed Burgess shale. An integrated approach has been used here to investigate the following: (1) high-resolution changes in water depth (sea level changes?) with stratigraphic position; (2) where exceptionally preserved fossils are most likely to occur; and (3) mineralogical indicators of sea level change, such as magnetic susceptibility and other rock magnetic properties. Rocks consist of limestones, argillaceous limestones, and finely-bedded mudstones (shales). Methods used here are: measurements of magnetic susceptibility, natural remanent magnetization, and viscous remanent magnetization; hysteresis loops; spectral gamma ray; coulometry to determine calcite content; X-ray diffraction; and field mapping. In these rocks, mineralogical analyses indicate primarily a 2-component system of calcite and terrigenous minerals, mainly illite. Magnetic susceptibility, gamma ray, and coulometry results strongly indicate that magnetic susceptibility stems primarily from the paramagnetic clay component, namely, illite. Thus, both magnetic susceptibility and gamma ray increase linearly with decreasing calcite content throughout the section studied. Deep-water shales yield very high values of gamma ray and magnetic susceptibility; by contrast, carbonates with low gamma ray and low magnetic susceptibilities were deposited in relatively shallow water. These results lead to the following conclusions: (1) changes in relative water depth have

  1. Anodic oxide growth on Zr in neutral aqueous solution

    Indian Academy of Sciences (India)

    Z Tun; J J Noël; D W Shoesmith

    2008-10-01

    Anodization and subsequent cathodic reactions on a thin-film sample of Zr were studied with in-situ neutron reflectometry (NR) and electrochemical impedance spectroscopy (EIS). The NR results during anodization showed the originally 485 Å thick Zr film generally behaved similar to a bulk electrode in neutral solution. The anodization ratio measured at applied potentials increased in steps of 0.5 V was somewhat higher than the value determined by coulometry, while the Pilling Bedworth ratio is in good agreement with published data. Thickening of the oxide layer, accelerated immediately after each potential increase, gradually decreased over several hours, but remained non-zero even after ∼ 12 h. The thickened oxide eventually cracked when its thickness reached ∼ 120 Å, causing loss of passivation. Surprisingly, neither the anodization ratio nor the Pilling Bedworth ratio showed any discontinuity at the time of oxide cracking, and the EIS behaviour remained qualitatively as before. This observation is taken as the evidence that the cracked and intact regions of the electrode behave more or less independently as parallel electrodes. When the potential was eventually switched to cathodic polarity, NR shows, as expected, that the effects of oxide cracking were irreversible. However, the electrode resistance recovered partially suggesting the cracks were rapidly plugged with newly formed oxide.

  2. Electrochemical studies of quinine in surfactant media using hanging mercury drop electrode: a cyclic voltammetric study.

    Science.gov (United States)

    Dar, Riyaz Ahmad; Brahman, Pradeep Kumar; Tiwari, Sweety; Pitre, Krishna Sadashiv

    2012-10-01

    The electrochemical behavior of quinine was investigated by cyclic voltammetry (CV) and square wave voltammetry (SWV) using surfactant. The reduction peak current of quinine increases remarkably in presence of 1% CTAB. Its electrochemical behavior is quasi-reversible in the Britton-Robinson buffers of pH 10.38 by exhibiting the well-defined single cathodic and anodic waves and the ratio of I(p)(a)/I(p)(c) approaching one at the scan rate of 500 mVs(-1). On the basis of CV, SWV and Coulometry, electrochemical reduction mechanism of quinine has been proposed which has shown that protonation occurs on the nitrogen of the quinoline moiety. Linearity was obtained when the peak currents (I(p)) were plotted against concentrations of quinine in the range of 30.0-230.0 ng mL(-1) with a detection limit of 0.132 ng mL(-1) in SWV and 90.0-630.0 ng mL(-1) with a detection limit of 0.238 ng mL(-1) in DPV. Fast and sensitive SWV has been applied for the quantitative analysis of quinine in bark of Cinchona sp. and in soft drinks and a good recovery was obtained. The accuracy and precision of the method are determined and validated statistically. No interferences from other food additives were observed. The relative standard deviation for intraday and interday assay was 0.89 and 0.73% (n=3) respectively.

  3. Evaluation of the ASTRA 4 new microprocessor-controlled electrolyte analyzer.

    Science.gov (United States)

    Hartmann, A E; Fillbach, J R

    1980-09-01

    A new programmable microprocessor-controlled multichannel chemistry analyzer, the Bechman ASTRA 4, was evaluated in an electrolyte configuration including sodium, potassium, chloride, and CO2. Sodium and potassium are analyzed with ion-selective electrodes, CO2 by differential rate pH measurement, and chloride by proportional coulometric titration, Day-to-day reproducibility studies yielded coefficients of variation of 0.8% for Na+, 1.2% for K+, 0.9% for Cl-, and 5.9% for CO2. Linearity was 100-200 mmol/l for Na+, 1.0-10.0 mmol/l for K+, 50-150 mmol/l for Cl+, and 5-50 mmol/l for CO2. There was excellent correlation between the ASTRA 4 and the comparison laboratory methodologies consisting of flame photometry, coulometry, and Beckman Chlorie/CO2 titrator. Performance of the ASTRA 4 was judged acceptable relative to requirements of medical usefulness. The instrument can be used as a routine electrolyte analyzer with a throughput of 60 samples an hour or as a stat analyzer with results obtained within 8.5 minutes. Each sample can be programmed for any combination of tests, and reagent is only consumed on those tests selected. Sample size is approximately 130 microliter for all four tests or reduced accordingly if fewer tests are selected.

  4. Synthesis, electrochemical, spectrophotometric and potentiometric studies of two azo-compounds derived from 4-amino-2-methylquinoline in ethanolic-aqueous buffered solutions

    Energy Technology Data Exchange (ETDEWEB)

    El-Attar, Mona A.; Ghoneim, Mohamed M. [Analytical Chemistry Research Unit, Chemistry Department, Tanta University (Egypt); Ismail, Iqbal M., E-mail: maema.2011@yahoo.com [Chemistry Department, Faculty of Science, King Abdul Aziz University, Jeddah (Saudi Arabia)

    2012-08-15

    Two azo-compounds, 2-methyl-4-(5-amino-2-hydroxy-phenylazo)-quinoline (2) and 2-methyl-4-(2-hydroxy-5-nitrophenylazo)-quinoline, derived from 4-amino-2-methylquinoline were synthesized. Their chemical structures were characterized and confirmed by means of elemental chemical analysis, infrared (IR) spectroscopy, {sup 1}H nuclear magnetic resonance (NMR) and mass spectrometry (MS). The electrochemical behavior of the starting compound (4-amino-2-methylquinoline) and of the two synthesized azo-derivatives was studied at the mercury electrode in the B-R universal buffer at various pH values (2-11.5) containing 40% (v/v) ethanol using dc-polarography, cyclic voltammetry and controlled-potential coulometry. Their electrode reaction pathways were elucidated and discussed. The dissociation constants (pKa) of the examined compounds, stability constants and stoichiometry of their complexes in solution with some transition metal ions (Co(II), Ni(II), Cu(II), La(III) and UO{sup 2+}{sub 2}) were determined. (author)

  5. Evidence and analysis of parallel growth mechanisms in Cu{sub 2}O films prepared by Cu anodization

    Energy Technology Data Exchange (ETDEWEB)

    Caballero-Briones, F., E-mail: fcaballerobriones@ub.ed [Department of Physical Chemistry, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); CIBER-BBN, Maria de Luna 11, 50018 Zaragoza (Spain); Palacios-Padros, A. [Department of Physical Chemistry, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Calzadilla, O. [Facultad de Fisica, Universidad de La Habana, San Lazaro y L, Colina Universitaria, 10400 Vedado, La Habana (Cuba); Sanz, Fausto, E-mail: fsanz@ub.ed [Institute for Bioengineering of Catalonia (IBEC), Edifici Helix, Baldiri i Reixac 15-21, 08028 Barcelona (Spain); Department of Physical Chemistry, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); CIBER-BBN, Maria de Luna 11, 50018 Zaragoza (Spain)

    2010-05-30

    We have studied the preparation of Cu{sub 2}O films by copper anodization in a 0.1 M NaOH electrolyte. We identified the potential range at which Cu{sup +} dissolution takes place then we prepared films with different times of exposure to this potential. The morphology, crystalline structure, band gap, Urbach energy and thickness of the films were studied. Films prepared with the electrode unexposed to the dissolution potential have a pyramidal growth typical of potential driven processes, while samples prepared at increasing exposure times to dissolution potential present continuous nucleation, growth and grain coalescence. We observed a discrepancy in the respective film thicknesses calculated by coulometry, atomic force microscopy and optical reflectance. We propose that anodic Cu{sub 2}O film formation involves three parallel mechanisms (i) Cu{sub 2}O nucleation at the surface, (ii) Cu{sup +} dissolution followed by heterogeneous nucleation and (iii) Cu{sup +} and OH{sup -} diffusion through the forming oxide and subsequent reaction in the solid state.

  6. Solvents' Critical Role in Nonaqueous Lithium-Oxygen Battery Electrochemistry.

    Science.gov (United States)

    McCloskey, B D; Bethune, D S; Shelby, R M; Girishkumar, G; Luntz, A C

    2011-05-19

    Among the many important challenges facing the development of Li-air batteries, understanding the electrolyte's role in producing the appropriate reversible electrochemistry (i.e., 2Li(+) + O2 + 2e(-) ↔ Li2O2) is critical. Quantitative differential electrochemical mass spectrometry (DEMS), coupled with isotopic labeling of oxygen gas, was used to study Li-O2 electrochemistry in various solvents, including carbonates (typical Li ion battery solvents) and dimethoxyethane (DME). In conjunction with the gas-phase DEMS analysis, electrodeposits formed during discharge on Li-O2 cell cathodes were characterized using ex situ analytical techniques, such as X-ray diffraction and Raman spectroscopy. Carbonate-based solvents were found to irreversibly decompose upon cell discharge. DME-based cells, however, produced mainly lithium peroxide on discharge. Upon cell charge, the lithium peroxide both decomposed to evolve oxygen and oxidized DME at high potentials. Our results lead to two conclusions; (1) coulometry has to be coupled with quantitative gas consumption and evolution data to properly characterize the rechargeability of Li-air batteries, and (2) chemical and electrochemical electrolyte stability in the presence of lithium peroxide and its intermediates is essential to produce a truly reversible Li-O2 electrochemistry.

  7. Electroreduction of the muscle relaxant drug dantrolene sodium at the mercury electrode and its determination in bulk form and pharmaceutical formulation.

    Science.gov (United States)

    Ghoneim, Enass Mohamed

    2007-10-01

    The electroreduction of the muscle relaxant drug dantrolene sodium at the mercury electrode has been studied in the Britton-Robinson universal buffer of pH 2.5-11.5 containing 20% (v/v) methanol by means of dc-polarography, cyclic voltammetry and controlled-potential coulometry. Its reduction took place via three irreversible cathodic steps in solutions of pH or =10 through the consumption of 10, 8 or 4 electrons, respectively. This behavior was attributed to the reduction of NO(2) group (1st and 2nd steps at pH or =10) and the -CH=N- double bond (3rd step at pH <10). Two polarographic procedures (direct current and differential-pulse modes) and three adsorptive cathodic stripping voltammetric procedures (linear-sweep, differential-pulse and square-wave modes) were described and successfully applied for quantification of dantrolene sodium in its bulk form and in pharmaceutical formulation (Dantrolex tablets).

  8. Formation of PbTe nanofilms by electrochemical atomic layer deposition (ALD)

    Energy Technology Data Exchange (ETDEWEB)

    Banga, Dhego O.; Vaidyanathan, Raman; Xuehai, Liang [Department of Chemistry, University of Georgia, Athens, GA 30602-2556 (United States); Stickney, John L. [Department of Chemistry, University of Georgia, Athens, GA 30602-2556 (United States)], E-mail: Stickney@chem.uga.edu; Cox, Stephen; Happeck, Uwe [Department of Physics and Astronomy, University of Georgia, Athens, GA 30602-2556 (United States)

    2008-10-01

    This article describes optimization of a cycle for the deposition of lead telluride (PbTe) nanofilms using electrochemical atomic layer deposition (ALD). PbTe is of interest for the formation of thermoelectric device structures. Deposits were formed using an ALD cycle on Au substrates, one atomic layer at a time, from separate solutions, containing Pb{sup 2+} or HTeO{sub 2}{sup +} ions. Single atomic layers were formed using surface limited reactions, referred to as underpotential deposition (UPD), so the deposition cycle consisted of alternating UPD of Te and Pb. The Pb deposition potential was maintained at -0.35 V throughout the 100 cycle-runs, while the Te deposition potential was ramped up from -0.55 V to -0.40 V over the first 20 cycles and then held constant for the remaining ALD cycles. Coulometry for the reduction of both Te and Pb indicated coverages near one monolayer, each cycle. Electron probe microanalysis (EPMA) indicated a uniform and stoichiometric deposit, with a Te/Pb ratio of 1.01. X-ray diffraction measurement showed that the thin films had the rock salt structure, with a preferential (2 0 0) orientation for the as formed deposits. No annealing was used. Infrared reflection absorption measurements of PbTe films formed with 50, 65, and 100 cycles indicated strong quantum confinement.

  9. Reference materials and interlaboratory comparison for actinide analysis

    Energy Technology Data Exchange (ETDEWEB)

    Hanssens, Alain; Viallesoubranne, Carole; Roche, Claude; Liozon, Gerard [Commissariat a l' Energie Atomique, Marcoule: BP 17171, 30207 Bagnols sur Ceze (France)

    2008-07-01

    Measurement quality is crucial for the safety of nuclear facilities and is a primary requirement for fissile material monitoring and accountancy. CETAMA (Cea Committee for the establishment of analysis methods), in collaboration with Cea and AREVA laboratories, fabricates certified reference materials and organizes interlaboratory comparison programs for plutonium and uranium assay in solution. A new plutonium metal measurement standard (MP3) is currently being prepared by Cea and is a subject of cooperative work in view of its certification and use by analysis laboratories. U and Pu interlaboratory comparisons are carried out at regular intervals on benchmark samples in coordination with working groups from French nuclear laboratories. These programs are supported by international cooperation. 'Chemical' methods (potentiometry, gravimetric analysis, etc.) generally provide the best accuracy. Coulometry is the benchmark technique for plutonium assay: its metrological qualities should be an incentive for wider use by laboratories performing precise control assays of plutonium as well as uranium. Gravimetric analysis provides excellent results for analysis of pure uranyl nitrate solutions. In view of its many advantages we encourage laboratories to employ this technique to assay pure U or Pu solutions. 'Physical' or 'physicochemical' methods are increasingly used, and their performance has improved. K-edge absorption spectrometry and isotope dilution mass spectrometry are capable of reaching measurement quality levels comparable to those of the best 'chemical' methods. (authors)

  10. First Orange Fluorescence Composite Film Based on Sm-Substituted Tungstophosphate and Its Electrofluorochromic Performance.

    Science.gov (United States)

    Gao, Wenmei; Yu, Tian; Du, Yu; Wang, Ruiqiang; Wu, Lixin; Bi, Lihua

    2016-05-11

    We chose a Sm-containing sandwich-type tungstophosphate K3Cs8[Sm(PW11O39)2]·10H2O (SmPW11) as a molecular dyad, which contains photoluminescence and electrochromism components in a skeletal structure, and investigated its electrofluorochromic performance both in solution and in composite films. First, the electrochemical activity and luminescence property of SmPW11 were studied in different pH solutions to determine the optimal pH solution medium; and then, the electrofluorochromic performance of SmPW11 was investigated under the optimized pH solution medium. Subsequently, the composite films containing SmPW11 were prepared on quartz substrates and conductive ITO substrates through a layer-by-layer (LbL) assembly method, using PDDA and PEI as molecular linkers. Characterization methods of the composite films include UV-vis spectra, fluorescence spectroscopy, cyclic voltammetry (CV), bulk electrolysis with coulometry, chronoamperometry, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Finally, in situ UV-vis and fluorescence spectroelectrochemical systems were used to research electrofluorochromic properties for the composite films under electrochemical modulation. The results indicate that the composite films display not only orange luminescence emission but also reversible orange luminescence switching behaviors manipulated by the redox process of tungstophosphate species PW11 via the energy transfer between the orange luminescence component Sm and electroreduced species of tungstophosphate PW11.

  11. Use of destructive and nondestructive methods of analysis for quality assurance at MOX fuel production in the Russia

    Energy Technology Data Exchange (ETDEWEB)

    Bibilashvili, Y.K.; Rudenko, V.S.; Chorokhov, N.A.; Korovin, Y.I.; Petrov, A.M.; Vorobiev, A.V.; Mukhortov, N.F.; Smirnov, Y.A.; Kudryavtsev, V.N. [A.A. Bochvar All-Russia Research Institute of Inorganic Materials (Russian Federation)

    2000-07-01

    Parameters of MOX fuel with various plutonium contents are considered from the point of view of necessity of their control for quality assurance. Destructive and nondestructive methods used for this purpose in the Russia are described: controlled potential coulometry for determination of uranium or/and plutonium contents, their ratio and oxygen factor; mass spectrometry for determination of uranium and plutonium isotopic composition; chemical spectral emission method for determination of contents of 'metal' impurities, boron and silicon, and methods of determination of gas forming impurities. Capabilities of nondestructive gamma-ray spectrometry techniques are considered in detail and results of their use at measurement of uranium and plutonium isotopic composition in initial dioxides, at determination of contents of uranium and plutonium, and uniformity of their distribution in MOX powder and pellets. The necessity of correction of algorithm of the MGA program is shown for using the program at analyses of gamma-ray spectra of MOX with low contents of low burnup plutonium. (authors)

  12. Preparation of novel core-shell nanoparticles by electrochemical synthesis

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Nanostructural gold/polyaniline core/shell composite particles on conducting electrode ITO were successfully prepared via electrochemical polymerization of aniline based on 4-aminothiophenol (4-ATP) capped Au nanoparticles. The new approach to the fabrication included three steps: preparation of gold nanoparticles as core by pulse electrodeposition; formation of ATP monolayer on the gold particle surface, which served as a binder and an initiator; polymerization of aniline monomer initiated by ATP molecules under controlled voltage lower than the voltammetric threshold of aniline polymerization, which assured the formation of polyaniline shell film occurred on gold particles selectively. Topographic images were also studied by AFM, which indicated the diameter of gold nanoparticles were around 250 nm. Coulometry characterization confirmed the shell thickness of polyaniline film was about 30 nm.A possible formation mechanism of the Au/polyaniline core-shell nanocomposites was also proposed. The novel as-prepared core-shell nanoparticles have potential application in constructing biosensor when bioactive enzymes are absorbed or embedded in polyaniline shell film.

  13. Diffuse Spectral Reflectance Records from the Northeast Pacific Oxygen Minimum Zone: Evidence for Rapid Shifts in Carbonate and Organic Carbon throughout the Holocene

    Science.gov (United States)

    Delvisico, J. G.; OConnell, S.; Ortiz, J. D.

    2002-05-01

    Sediment cores collected within the Oxygen Minimum Zone (O2 Soledad Basin, desirable for its high sedimentation rates (100-120cm/kyr) and its 200 m sill depth. We maintain the hypothesis that variations in carbonate and organic carbon seen through the Diffuse Spectral Reflectance (DSR) will preferentially show the effects of local production on the spatial/temporal extent of the Oxygen Minimum Zone due to the circulation restrictions imposed on the basin by its shallow sill depth. The summer's work involved compiling a composite proxy record of variations in organic carbon through R-mode factor analysis of the Diffuse Spectral Reflectance signal, which was then further constrained through coulometry to provide confidence points for reflectance-derived proxy values. Through the compilation of the five piston core records, a continuous, high frequency climatic proxy record of changes in productivity was constructed over the past 15 Ka. Organic carbon shifts within the Soledad record also contain a periodicity within the time scale bounds of the present day Pacific Decadal Oscillation (20-50 year quasi-cyclicity) discerned initially from various forms of autospectral time series analysis, suggesting a connection between the two processes. The Soledad DSR record has also shown strong positive correlations to other high-resolution global paleoclimate proxy records, through which we hope to further elucidate rapid climate teleconnections between high and low latitude climate instability during the past 15 Ka.

  14. Electrochemical reduction of the biliverdin-serum albumin complex as monitored by absorption and circular dichroism spectroscopy.

    Science.gov (United States)

    Claret, J; Ibars, O; Lang, K; Trull, F R; Lightner, D A

    1995-02-23

    The cathodic reduction at the mercury electrode of a biliverdin IX alpha-serum albumin complex at physiological pH in an aqueous buffer containing percentages of DMSO ranging from 4% to 20% is studied by cyclic voltametry and controlled potential coulometry. The progression of pigment disappearance and the (stereochemical) nature of the product are monitored by chromatography, UV-visible absorption and circular dichroism spectroscopy. Upon reduction, albumin-bound biliverdin IX alpha, with a slight preference for the P-helicity, affords the corresponding bound bilirubin IX alpha -with an M-chirality conformation. The complex is reduced at -0.64 V (vs. SCE; 8% DMSO), only a little shifted compared to reduction of free biliverdin IX alpha under the same conditions. In contrast, an analogous bilirubin IX alpha-serum albumin complex is essentially inert towards cathodic reduction under conditions where free bilirubin IX alpha is reduced, indicating a better shielding by the protein of the bilirubin IX alpha molecule from the electrode surface. The presence of relative position (as in the biliverdins IX alpha and XIII alpha) or absence (as in mesobiliverdin IX alpha) of vinyl groups in the pigment does not have a significant effect upon its electroreduction behaviour, indicating that the process is not sensitive to the subtle differences imposed by vinyl groups upon the structure of the corresponding biliverdin-albumin complexes.

  15. Electrochemistry "Discovery" Course for Undergraduates

    Science.gov (United States)

    May, Michael Alan; Gupta, Vijay K.

    1997-07-01

    We developed a chemistry selected topics course at Central State University, "Introduction to Laboratory Techniques in Electrochemistry" to: (1) give undergraduates hands-on experience with electrochemical measurements, (2) prepare students for summer research in Fuel Cell and Battery technology. Since students "learn by doing", the course is suitable for undergraduates from sophomore to senior levels. Students complete 6 laboratories, based on a "less is more" philosophy which emphasizes analytic and creative process rather than mandatory topical coverage. Eight electrochemical experiments are available: Construction of Zinc-Copper battery stacks, Lead Acid Battery discharge-charge cycles, Conductimetric titration of aspirin with Ammonium Hydroxide, Ion Selective Electrode determination of Fluoride in water, Cyclic Voltammetry of Potassium Ferricyanide solution, Cyclic Voltammetry of Sulfuric acid on Platinum working electrode, Anodic Stripping Voltammetry of Lead ion in solution, Differential Pulse Polarography of Lead ion in solution. Topics discussed in lecture include: chemical definitions, electrical definitions, Oxidation-Reduction reactions, Electrochemical series, Electrodes, Electrochemical Cells, direct Coulometry, electrolysis, electrochemical process efficiency, equilibrium Potentiometry, real Cell Voltages, Ion Selective Electrode types and designs, reference electrode designs, working electrode materials, pH buffers, Cyclic Voltammetry, Anodic Stripping Voltammetry, Polarography, differential pulse Polarography, and simple electrochemical instrumentation circuits.

  16. DF—1型电化学分析仪

    Institute of Scientific and Technical Information of China (English)

    王庆璋; 王维新

    1985-01-01

    Model DF-1 electrochemical analyzer is a many-purpose electrochemical instrumentation with following five functional select switches for operating conditions: cathodic /anodie polarization; single/cycle sean;two/three electrodes system;direct/derivative output;normal/differential mode. Consequently they can be combined into several working manners, result in different experimental methods as consistent with desire. This instrument has manifold compensator and adjuster with a wide-range, so that the sensitivity and the signal graph have been able to improve. In addition, the instrument incorporates a strip-chart recorder and an exact timer. It is also equipped with electrochemical bench and a set of electrodes including the rotating glassy carbon electrode, gold plate electrode, silver plate electrode, mercury coated silver base electrode, hanging mercury electrode etc. In order to broaden the field of its application, all units of the instrument can be unitized, but each and every can be also used independently. The instrument is applicable to polarography, voltammetry, potentiometric stripping, potentiostatic electrolysis,differential technique, coulometry, linear polarization method, cycle voltammetry, passivation curve, and some other electrochemical technique, which have need for electrochemical cell with two, three,or four electrodes. This paper describes the design fundament, feature and specification of the electrochemical analyzer, and finally gives laboratory application some experimental examples.

  17. Elemental and organic carbon in flue gas particles of various wood combustion systems

    Energy Technology Data Exchange (ETDEWEB)

    Gaegauf, C.; Schmid, M.; Guentert, P.

    2005-12-15

    The airborne particulate matter (PM) in the environment is of ever increasing concern to authorities and the public. The major fractions of particles in wood combustion processes are in the size less than 1 micron, typically in the range of 30 to 300 nm. Of specific interest is the content of the elemental carbon (EC) and organic carbon (OC) in the particles since these substances are known for its particular potential as carcinogens. Various wood combustion systems have been analysed (wood chip boiler, pellet boiler, wood log boiler, wood stove and open fire). The sampling of the particles was done by mean of a multi-stage particle sizing sampler cascade impactor. The impactor classifies the particles collected according to their size. The 7 stages classify the particles between 0.4 and 9 microns aerodynamic diameter. The analytical method for determining the content of EC and OC in the particles is based on coulometry. The coulometer measures the conductivity of CO{sub 2} released by oxidation of EC in the samples at 650 {sup o}C. The OC content is determined by pyrolysis of the particle samples in helium atmosphere.

  18. Determination of the thickness of rhodium cover and major elements in gold and platinum jewelry by XRF%X射线荧光光谱法测试金铂饰品中铑覆盖层厚度及主体元素

    Institute of Scientific and Technical Information of China (English)

    龙建; 王丽敏; 黄佩英

    2015-01-01

    X ray fluorescence( XRF) is applied to determine the thickness of rhodium cover and major elements in gold and platinum jewelry without damaging them by comparing standard rhodium cover slice, standard gold alloy slice and standard platinum alloy slice. The test result is verified by comparing the results of classic coulometry, ICP subtraction and fire assay, proving to be very accurate.%采用X射线荧光光谱法,通过对比标准铑覆盖层片、标准金合金片和标准铂合金片,在非破坏性的前提下,同时测定金、铂饰品中的铑镀层厚度及主体元素。采用该方法的测试结果与经典库仑法、ICP差减法和火试金法的测试结果进行了对比验证,该方法测试结果具有较高的准确度。

  19. Voltammetric oxidation of Hantzsch 1,4-dihydropyridines in protic media: substituent effect on positions 3,4,5 of the heterocyclic ring

    Energy Technology Data Exchange (ETDEWEB)

    Arguello, J.; Nunez-Vergara, L.J.; Sturm, J.C.; Squella, J.A. [University of Chile, Santiago (Chile). Bioelectrochemistry Laboratory

    2004-10-30

    A detailed study was done of the electrochemical oxidation of some 1,4-dihydropyridine (1,4-DHP) derivatives in order to determine the influence of the substituents in the heterocyclic ring. Two types of derivatives were synthesized, namely, 3,5-(substituted)-4-(5{sup '}-nitro-2'-furyl)-l,4-DHP for series A, and 3,5-dicarboethoxy-4-(substituted or non-substituted)-l,4-DHP for series B. Voltammetry, coulometry, controlled potential electrolysis, UV-vis spectroscopy and GC-MS techniques were employed to collect data that permitted to postulate oxidation mechanisms in a protic medium. In acid media, at pH < 4, all derivatives follow oxidation mechanisms obeying the ECE sequence. However, at pH > 4, series A derivatives follow an ECEC sequence, while series B derivatives obey a DISP1 mechanism. In both cases, the uptake of proton at N-1 by the OH{sup -} ion of the media was the rate-determining step. (author)

  20. Environmental Sensing of Aquatic Systems at the University of Geneva.

    Science.gov (United States)

    Bakker, Eric; Tercier-Waeber, Mary-Lou; Cherubini, Thomas; Crespi, Miquel Coll; Crespo, Gastón A; Cuartero, Maria; Afshar, Majid Ghahraman; Jarolimova, Zdenka; Jeanneret, Stéphane; Mongin, Sandrine; Néel, Bastien; Pankratova, Nadezda; Touilloux, Romain; Xie, Xiaojiang; Zhai, Jingying

    2014-11-01

    Aquatic environments are complex living systems where biological and chemical constituents change rapidly with time and space and may exhibit synergistic interactions. To understand these processes, the traditional approach based on a typically monthly collection of samples followed by laboratory analysis is not adequate. It must be replaced by high-resolution autonomous in situ detection approaches. In our group at the University of Geneva, we aim to develop and deploy chemical sensor probes to understand complex aquatic systems. Most research centers around electrochemical sensing approaches, which involves: stripping voltammetry at gel-coated microelectrode arrays for direct measurements of bioavailable essential or toxic trace metals; direct potentiometry for the measurement of nutrients and other species involved in the nitrogen and carbon cycles; online desalination for oceanic measurements; the development of robust measurement principles such as thin layer coulometry, and speciation analysis by tandem electrochemical detection with potentiometry and dynamic electrochemistry. These fundamental developments are combined with instrument design, both in-house and with external partners, and result in field deployments in partnership with environmental researchers in Switzerland and the European Union.

  1. Physical and chemical characterization of cerium(IV) oxide nanoparticles.

    Science.gov (United States)

    Cepriá, Gemma; Córdova, Walvin R; Céspedes, Oscar; Sánchez-García, Laura; Ferrer, Pilar; Gianolio, Diego; Castillo, Juan R

    2016-09-01

    Chemical composition, size and structure of the nanoparticle are required to describe nanoceria. Nanoparticles of similar size and Ce(III) content might exhibit different chemical behaviour due to their differences in structure. A simple and direct procedure based on affordable techniques for all the laboratories is presented in this paper. The combination of Raman and UV-vis spectroscopy and particle impact coulometry (PIC) allows the characterization of nanoceria of small size from 4 to 65 nm at a concentration from micromolar to nanomolar, a concentration range suitable for the analysis of lab-prepared or commercial nanoparticle suspensions, but too high for most analytical purposes aimed at nanoparticle monitoring. While the PIC limits of size detection are too high to observe small nanoparticles unless catalytic amplification is used, the method provides a simple means to study aggregation of nanoparticles in the media they are needed to be dispersed for each application. Raman spectroscopy provided information about structure of the nanoparticle, and UV-vis about their chemical behaviour against some common reducing and oxidizing agents. Graphical Abstract To characterize nanoceria it is necessary to provide information about the shape, size and structure of the nanoparticles as well as the chemical composition.

  2. Electrochemical Behavior of Quinoxalin-2-one Derivatives at Mercury Electrodes and Its Analytical Use

    Directory of Open Access Journals (Sweden)

    Milan Zimpl

    2012-01-01

    Full Text Available Derivatives of quinoxalin-2-one are interesting compounds with potential pharmacological activity. From this point of view, understanding of their electrochemical behavior is of great importance. In the present paper, a mechanism of electrochemical reduction of quinoxalin-2-one derivatives at mercury dropping electrode was proposed. Pyrazine ring was found to be the main electroactive center undergoing a pH-dependent two-electron reduction process. The molecule protonization of nitrogen in the position 4 precedes the electron acceptance forming a semiquinone radical intermediate which is relatively stable in acidic solutions. Its further reduction is manifested by separated current signal. A positive mesomeric effect of the nonprotonized amino group in the position 7 of the derivative III accelerates the semiquinone reduction yielding a single current wave. The suggested reaction mechanism was verified by means of direct current polarography, differential pulse, cyclic and elimination voltammetry, and coulometry with subsequent GC/MS analysis. The understanding of the mechanism was applied in developing of analytical method for the determination of the studied compounds.

  3. Determination of copper(II) in the dairy product by an electrochemical sensor based on click chemistry.

    Science.gov (United States)

    Qiu, Suyan; Xie, Lidan; Gao, Sen; Liu, Qida; Lin, Zhenyu; Qiu, Bin; Chen, Guonan

    2011-11-30

    Herein, a novel sensitive electrochemical sensor for copper(II) based on Cu(I) catalyzed alkyne-azide cycloaddition reaction (CuAAC) is described. The catalyst of Cu(I) species is derived from electrochemical reduction of Cu(II) through bulk electrolysis (BE) with coulometry technique. The propargyl-functionalized ferrocene (propargyl-functionalized Fc) is covalently coupled onto the electrode surface via CuAAC reaction and forms propargyl-functionalized Fc modified gold electrode, which allows a good and stable electrochemical signal. The change of current at peak (dI), detected by differential pulse voltammetry (DPV), exhibits a linear response to the logarithm of Cu(II) concentration in the range of 1.0×10(-14)-1.0×10(-9) mol L(-1). It is also found that the proposed sensor has a good selectivity for copper(II) assay even in the presence of other common metal ions. Additionally, the proposed method has been applied to determine copper(II) in the dairy product (yoghurt) with satisfactory results.

  4. Development of ultra-high sensitive and selective electrochemiluminescent sensor for copper(II) ions: a novel strategy for modification of gold electrode using click chemistry.

    Science.gov (United States)

    Qiu, Suyan; Gao, Sen; Zhu, Xi; Lin, Zhenyu; Qiu, Bin; Chen, Guonan

    2011-04-21

    A promising and highly sensitive electrochemiluminescence (ECL) sensor for the detection of Cu(2+) based on Cu(+)-catalyzed click reaction is described in this paper. Firstly, 1-azidoundecan-11-thiol was assembled on the Au electrode surface via a simple thiol-Au reaction, then the propargyl-functionalized Ru(bpy)(3)(2+)-doped SiO(2) nanoparticles (Ru-SNPs) ECL probe was covalently coupled on the electrode surfaces via click chemistry. Cu(+), the catalyst for click chemistry, is derived from the electrolytic reduction of Cu(2+)via the Bulk Electrolysis with coulometry (BE) technique and without any reductants. It is found that the ECL intensity detected from the electrode surface has a linear relationship with the logarithm of Cu(2+) concentration in the range of 1.0 × 10(-15) to 1.0 × 10(-11) M with a detection limit of 1.0 × 10(-16) M. Also, the method is highly specific even in the presence of high concentrations of other metal cations. It has been applied to detect trace Cu(2+) in complex samples (hepatoma cell) without sample treatment.

  5. Se adlattices formed on Au(100), studies by LEED, AES, STM and electrochemistry

    Science.gov (United States)

    Huang, Baoming M.; Lister, Tedd E.; Stickney, John L.

    1997-12-01

    Ordered selenium atomic layers have been formed electrochemically on Au(100) at a series of coverages. Cyclic voltammetry and coulometry were used to study the deposition process, and to determine the corresponding coverages of a number of Se structures. Structures, with Se coverages of 0.25, 0.33, 0.5, and 0.89 monolayers, were identified using ultra high vacuum — electrochemical techniques as well as scanning tunneling microscopy. The corresponding unit cells of those structures were: p(2 × 2), (2 × √10), c(2 × 2), and a mostly (3 × √10), composed of close-packed Se 8 rings. Pit formation, associated with the formation of the densely packed Se 8 ring structure, was observed. They are reminiscent of pits observed in self-assembled monolayers of alkane thiols on Au surfaces. The pits disappeared as the structure, composed of Se rings, was converted to lower coverage structures, such as the 0.25 monolayer p(2 × 2), via anodic stripping. Se atomic layers were formed electrochemically in three ways: direct reduction from a HSeO -3 solution; anodic stripping of previously formed bulk Se; or cathodic stripping of previously formed bulk Se. All three methods resulted in equivalent atomic layer structures on the Au(100) surface, but with some variation in the homogeneity and distribution of particular structures.

  6. New insights into the electrochemical behavior of acid orange 7: Convergent paired electrochemical synthesis of new aminonaphthol derivatives

    Science.gov (United States)

    Momeni, Shima; Nematollahi, Davood

    2017-02-01

    Electrochemical behavior of acid orange 7 has been exhaustively studied in aqueous solutions with different pH values, using cyclic voltammetry and constant current coulometry. This study has provided new insights into the mechanistic details, pH dependence and intermediate structure of both electrochemical oxidation and reduction of acid orange 7. Surprisingly, the results indicate that a same redox couple (1-iminonaphthalen-2(1H)-one/1-aminonaphthalen-2-ol) is formed from both oxidation and reduction of acid orange 7. Also, an additional purpose of this work is electrochemical synthesis of three new derivatives of 1-amino-4-(phenylsulfonyl)naphthalen-2-ol (3a–3c) under constant current electrolysis via electrochemical oxidation (and reduction) of acid orange 7 in the presence of arylsulfinic acids as nucleophiles. The results indicate that the electrogenerated 1-iminonaphthalen-2(1 H)-one participates in Michael addition reaction with arylsulfinic acids to form the 1-amino-3-(phenylsulfonyl)naphthalen-2-ol derivatives. The synthesis was carried out in an undivided cell equipped with carbon rods as an anode and cathode.

  7. Electroanalysis of dapsone, an anti-leprotic drug.

    Science.gov (United States)

    Manisankar, P; Sarpudeen, A; Viswanathan, S

    2001-12-01

    The electrochemical oxidation and adsorption of dapsone, an anti-leprotic drug were studied in aqueous alcohol medium at a stationary glassy carbon electrode. Cyclic voltammetry studies showed one well-defined oxidation peak in the potential range 1.2-1.9 V at pH conditions 1.0, 4.0, 7.0, 9.2 and 13.0. The oxidation was irreversible and exhibited diffusion controlled adsorption. Controlled potential coulometry revealed one electron oxidation of the amino group in the molecule. A systematic study of the experimental parameters that affect the squarewave stripping response was carried out and the optimized experimental conditions were arrived at. A calibration plot was derived for the determination of the compound in solution. This method was used for the determination of dapsone in tablets and urine. The limits of determination was 0.0036 and 3.56 mg/ml and the relative standard deviation (n=10) was 4 ppt (0.4%) at a concentration level 0.100 mg/ml.

  8. Study of the oxygen reduction reaction on stainless steel materials in natural seawater. Influence of the bio-film on corrosion processes; Reaction de reduction de l'oxygene sur les aciers inoxydables en eau de mer naturelle. Influence du biofilm sur les processus de corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Le Bozec, N

    2000-01-15

    Bio-film development on stainless steels immersed in natural seawater can have prejudicial consequences on the resistance of these materials to corrosion. The goal of the present study was to get more precise information on the corrosion processes, and especially on the oxygen reduction reaction. As the reaction is linked to the stainless steel surface state, the characterisation of the oxides films (composition, structure, thickness...) is essential to understand the mechanisms and the oxygen reduction kinetic. The first aim of the study has been to correlate the oxygen reduction processes with the characteristics of the oxides layer as a function of the alloy surface treatment (mechanical polishing, electrochemical passivation and pre-reduction, chemical treatment with some acids or with hydrogen peroxide). The second stage has consisted in following the evolution of the oxygen reduction processes and of the characteristics of the oxides layer with the aging of stainless steels in natural and artificial sea-waters. One major bio-film effect appears to be the production of hydrogen peroxide at a concentration level which induces modifications of the oxides layers and, consequently, of the evolution of the oxygen reduction kinetics as well as of the open circuit potential. Electrochemical techniques (voltammetric analysis at rotating disk and ring-disk electrodes, coulometry) combined with a surface analytical method by X-ray photoelectron spectroscopy have been used. The characterisation of the bio-film required the use of microscopy (scanning electronic microscopy, epi-fluorescence microscopy) and microbiological methods (cultures). The in-situ detection of hydrogen peroxide formed inside the bio-film has been performed with a micro-electrode and the results were confirmed with enzymatic methods. (author)

  9. New Signal Readout Principle for Solid-Contact Ion-Selective Electrodes.

    Science.gov (United States)

    Vanamo, Ulriika; Hupa, Elisa; Yrjänä, Ville; Bobacka, Johan

    2016-04-19

    A novel approach to signal transduction concerning solid-contact ion-selective electrodes (SC-ISE) with a conducting polymer (CP) as the solid contact is investigated. The method presented here is based on constant potential coulometry, where the potential of the SC-ISE vs the reference electrode is kept constant using a potentiostat. The change in the potential at the interface between the ion-selective membrane (ISM) and the sample solution, due to the change in the activity of the primary ion, is compensated with a corresponding but opposite change in the potential of the CP solid contact. This enforced change in the potential of the solid contact results in a transient reducing/oxidizing current flow through the SC-ISE. By measuring and integrating the current needed to transfer the CP to a new state of equilibrium, the total cumulated charge that is linearly proportional to the change of the logarithm of the primary ion activity is obtained. In this work, different thicknesses of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonate) (PSS) were used as solid contact. Also, coated wire electrodes (CWEs) were included in the study to show the general validity of the new approach. The ISM employed was selective for K(+) ions, and the selectivity of the membrane under implementation of the presented transduction mechanism was confirmed by measurements performed with a constant background concentration of Na(+) ions. A unique feature of this signal readout principle is that it allows amplification of the analytical signal by increasing the capacitance (film thickness) of the solid contact of the SC-ISE.

  10. O/M ratio measurement in pure and mixed oxide fuels - where are we now?

    Energy Technology Data Exchange (ETDEWEB)

    Rubin, J.; Chidester, K.; Thompson, M. [Los Alamos National Lab., NM (United States)

    2001-07-01

    The scale-down in the US and Russian nuclear weapons stockpiles has produced a surplus of weapons grade plutonium and highly enriched uranium. The incorporation into mixed-oxide fuel (MOX) is one of the currently favored routes for surplus weapons-grade plutonium. The use of MOX as a nuclear reactor fuel is well established, particularly in Europe and Japan but not in the US. The primary purpose of this investigation was to evaluate existing analytical techniques for their applicability to O/M (oxygen-to-metal ratio) measurements of MOX derived from excess weapons plutonium. The second objective of this investigation was to bring up-to-date the literature on O/M measurement methods, which has not been undertaken in over 20 years. There are several classification schemes that can be used to organize O/M measurement methods. The most popular schemes are based on (a) whether the analysis is performed in solution (wet chemical) or on solid material (dry), and (b) whether the concentration of major constituents are analyzed directly (direct) or are inferred (indirect). Solid state coulometric titration is currently used extensively in studies of phase equilibria, defect chemistry, thermochemical measurement of oxides, including ferrites. Regardless of which indirect method is used (solid state coulometric titration or thermogravimetry), a primary, direct method will also be required for the establishment of the MO{sub 2} reference state, determination of method bias, and periodic calibration. It was recommended that the following direct method be adapted for this purpose: oxygen measurement by inert gas fusion/carbon reduction, and total U, Pu by controlled potential coulometry. In a table are listed the experimental values of accuracy for about 30 O/M methods. (A.C.)

  11. Hierarchical Porous Carbon Spheres for High-Performance Na-O2 Batteries.

    Science.gov (United States)

    Sun, Bing; Kretschmer, Katja; Xie, Xiuqiang; Munroe, Paul; Peng, Zhangquan; Wang, Guoxiu

    2017-04-04

    As a new family member of room-temperature aprotic metal-O2 batteries, Na-O2 batteries, are attracting growing attention because of their relatively high theoretical specific energy and particularly their uncompromised round-trip efficiency. Here, a hierarchical porous carbon sphere (PCS) electrode that has outstanding properties to realize Na-O2 batteries with excellent electrochemical performances is reported. The controlled porosity of the PCS electrode, with macropores formed between PCSs and nanopores inside each PCS, enables effective formation/decomposition of NaO2 by facilitating the electrolyte impregnation and oxygen diffusion to the inner part of the oxygen electrode. In addition, the discharge product of NaO2 is deposited on the surface of individual PCSs with an unusual conformal film-like morphology, which can be more easily decomposed than the commonly observed microsized NaO2 cubes in Na-O2 batteries. A combination of coulometry, X-ray diffraction, and in situ differential electrochemical mass spectrometry provides compelling evidence that the operation of the PCS-based Na-O2 battery is underpinned by the formation and decomposition of NaO2 . This work demonstrates that employing nanostructured carbon materials to control the porosity, pore-size distribution of the oxygen electrodes, and the morphology of the discharged NaO2 is a promising strategy to develop high-performance Na-O2 batteries. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Selective nonenzymatic bilirubin detection in blood samples using a Nafion/Mn-Cu sensor.

    Science.gov (United States)

    Noh, Hui-Bog; Won, Mi-Sook; Shim, Yoon-Bo

    2014-11-15

    The specific detection of biological organics without the use of an enzyme is challenging, and it is crucial for analytical and clinical chemistry. We report specific nonenzymatic bilirubin detection through the catalytic oxidation of bilirubin molecule on the Nafion/Mn-Cu surface. The catalytic ability, true surface area, morphology, crystallinity, composition, and oxidation state of the sensor surface were assessed using voltammetry, coulometry, XPS, XRD, Brunauer-Emmett-Teller (BET), SEM, EDXS, and TOF-SIMS experiments. The results showed that the surface was composed of microporous Mn-Cu bimetallic crystal in flake shape with a large BET surface area (3.635 m(2)g(-1)), where the surface area and crystallinity mainly affected the sensor performance. Product analysis of the catalytic reaction on the sensor probe revealed a specific two-electron oxidation of dipyrromethane moiety to dipyrromethene in the bilirubin molecule. Experimental variables affecting the analysis of bilirubin were optimized in terms of probe composition, temperature, pH, and potential. At the optimized condition, the dynamic range was between 1.2 μM and 0.42 mM, which yielded the equation of ΔI (μA)=(1.03 ± 0.72)+(457.0 ± 4.03) [C] (mM) with 0.999 of correlation coefficient, and the detection limit was 25.0 ± 1.8 nM (n=5, k=3). The stability test, interference effects, and analysis of real clinical samples, human whole blood and certified serum samples were demonstrated to confirm the reliability of the proposed bilirubin sensor.

  13. An innovative spectroelectrochemical reflection cell for rapid protein electrochemistry and ultraviolet/visible/infrared spectroscopy.

    Science.gov (United States)

    Bernad, Sophie; Mäntele, Werner

    2006-04-15

    A novel electrochemical reflection cell combining electrochemical techniques and spectroscopy which uses a solid gold working electrode as an optical mirror is described. This cell can be used at path lengths as low as a few micrometers and thus is suitable for ultraviolet/visible (UV/Vis) and infrared spectroscopy even for aqueous solutions and suspensions. The cell was designed for small sample volumes of only a few microliters, thus reducing the effort for sample preparation. Due to the short path length of some micrometers, the entire volume is within the Nernst diffusion layer, hence resulting in fast equilibration. Evaluation of the technique is described with direct electrochemistry of horse heart cytochrome c at the gold electrode modified with 4,4'-dithiodipyridine. Cyclic voltammograms indicate rapid and reversible electrochemistry with the correct midpoint potential (52 mV vs Ag/AgCl/3 M KCl). Chronoamperometry and coulometry confirm rapid and complete oxidation and reduction; the cell volume can be entirely fully reduced within less than 10-20 s. Spectroscopy in the UV/Vis region, with potentials at the working electrode stepped between -390 and 390 mV, show perfect titration of the cytochrome c heme bands. A Nernst fit of the alpha band absorption, with redox potential Em and number of electrons n left as parameters, yields a midpoint potential of 49 mV and n=0.9. The potential of this cell in the investigation of biological electron transfer reactions and in the study of bioenergetic systems is discussed.

  14. Detection, characterization and quantification of inorganic engineered nanomaterials: A review of techniques and methodological approaches for the analysis of complex samples.

    Science.gov (United States)

    Laborda, Francisco; Bolea, Eduardo; Cepriá, Gemma; Gómez, María T; Jiménez, María S; Pérez-Arantegui, Josefina; Castillo, Juan R

    2016-01-21

    The increasing demand of analytical information related to inorganic engineered nanomaterials requires the adaptation of existing techniques and methods, or the development of new ones. The challenge for the analytical sciences has been to consider the nanoparticles as a new sort of analytes, involving both chemical (composition, mass and number concentration) and physical information (e.g. size, shape, aggregation). Moreover, information about the species derived from the nanoparticles themselves and their transformations must also be supplied. Whereas techniques commonly used for nanoparticle characterization, such as light scattering techniques, show serious limitations when applied to complex samples, other well-established techniques, like electron microscopy and atomic spectrometry, can provide useful information in most cases. Furthermore, separation techniques, including flow field flow fractionation, capillary electrophoresis and hydrodynamic chromatography, are moving to the nano domain, mostly hyphenated to inductively coupled plasma mass spectrometry as element specific detector. Emerging techniques based on the detection of single nanoparticles by using ICP-MS, but also coulometry, are in their way to gain a position. Chemical sensors selective to nanoparticles are in their early stages, but they are very promising considering their portability and simplicity. Although the field is in continuous evolution, at this moment it is moving from proofs-of-concept in simple matrices to methods dealing with matrices of higher complexity and relevant analyte concentrations. To achieve this goal, sample preparation methods are essential to manage such complex situations. Apart from size fractionation methods, matrix digestion, extraction and concentration methods capable of preserving the nature of the nanoparticles are being developed. This review presents and discusses the state-of-the-art analytical techniques and sample preparation methods suitable for

  15. Electrochemical Study of Iodide in the Presence of Phenol and o-Cresol: Application to the Catalytic Determination of Phenol and o-Cresol

    Directory of Open Access Journals (Sweden)

    Davood Nematollahi

    2004-11-01

    Full Text Available Abstract: The electrochemical oxidation of iodide in the presence of phenol and o-cresol was investigated at a glassy carbon electrode in buffered media by cyclic voltammetry, linear sweep voltammetry and controlled–potential coulometry. The experimental results indicate that the phenol and o-cresol convert to their derivatives after participating in a halogenation coupled reaction (quasi-catalytic reaction following the oxidation of iodide to iodine. The concentrations of phenol and o-cresol have been determined in aqueous solutions according to the linear dependence of quasi-catalytic peak currents with the concentration. The calibration graphs show two linear sections of 0.0 to 1.0×10-4 M and 2.0×10-4 to 1.0 ×10-3 M for phenol and 4.2×10-5 to 1.0×10-4 M and 2.0×10-4 to 1.0×10-3 M for o-cresol. The theoretical detection limits and the relative standard deviations for ten measurements of phenol and o-cresol are 1.125×10-5 M, 1.06% and 4.201×10-5 M, 1.44%, respectively.

  16. Electrochemical atomic layer deposition of copper nanofilms on ruthenium

    Science.gov (United States)

    Gebregziabiher, Daniel K.; Kim, Youn-Geun; Thambidurai, Chandru; Ivanova, Valentina; Haumesser, Paul-Henri; Stickney, John L.

    2010-04-01

    As ULSI scales to smaller and smaller dimensions, it has become necessary to form layers of materials only a few nm thick. In addition, trenches are now being incorporated in ULSI formation which require conformal coating and will not be amenable to CMP. Atomic layer deposition (ALD) is being developed to address such issues. ALD is the formation of materials layer by layer using self-limiting reactions. This article describes the formation of Cu seed layers (for the Cu damascene process) on a Ru barrier layer. The deposit was formed by the electrochemical analog of ALD, using electrochemical self-limiting reactions which are referred to as underpotential deposition (UPD). Monolayer restricted galvanic displacement was used to form atomic layers of Cu. First Pb UPD was deposited, forming a sacrificial layer, and then a Cu +2 solution was flushed into the cell and Pb was exchanged for Cu. A linear dependence was shown for Cu growth over 8 ALD cycles, and STM showed a conformal deposition, as expected for an ALD process. Relative Cu coverages were determined using Auger electron spectroscopy, while absolute Cu coverages were obtained from coulometry during oxidative stripping of the deposits. Use of a Cl - containing electrolyte results in Cu deposits covered with an atomic layer of Cl atoms, which have been shown to protect the surfaced from oxidation during various stages of the deposition process. The 10 nm thick Ru substrates were formed on Si(1 0 0) wafers, and were partially oxidized upon receipt. Electrochemical reduction, prior to Cu deposition, removed the oxygen and some traces of carbon, the result of transport. Ion bombardment proved to clean all oxygen and carbon traces from the surface.

  17. Simultaneous determination of five common additives in insulating mineral oils by high-performance liquid chromatography with ultraviolet and coulometric detection.

    Science.gov (United States)

    Bruzzoniti, Maria Concetta; Sarzanini, Corrado; Rivoira, Luca; Tumiatti, Vander; Maina, Riccardo

    2016-08-01

    Dielectric mineral oils are used to impregnate power transformers and large electrical apparatus, acting as both liquid insulation and heat dissipation media. Antioxidants and passivators are frequently added to mineral oils to enhance oxidation stability and reduce the electrostatic charging tendency, respectively. Since existing standard test methods only allow analysis of individual additives, new approaches are needed for the detection of mixtures. For the first time we investigate and discuss the performance of analytical methods, which require or do not require extraction as sample pretreatment, for the simultaneous reversed-phase high-performance liquid chromatography determination of passivators (benzotriazole, Irgamet(®) 39) and antioxidants (N-phenyl-1-naphtylamine, 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol), chosen for their presence in marketed oils. Quick easy, cheap, effective, rugged and safe and solid phase extractions were evaluated as sample pretreatments. Direct sample-injection was also studied. Ultraviolet spectrophotometry and direct-current coulometry detection were explored. As less prone to additive concentrations variability, the direct-injection high-performance liquid chromatography with ultraviolet and coulometric detection method was validated through comparison with Standard Method IEC 60666 and through an ASTM interlaboratory proficiency test. Obtained detection limits are (mg kg(-1) ): benzotriazole (2.8), Irgamet(®) 39 (13.8), N-phenyl-1-naphtylamine (11.9), 2,6-di-tert-butylphenol (13.1), 2,6-di-tert-butyl-p-cresol (10.2). Simultaneous determination of selected additives was possible both in unused and used oils, with good precision and accuracy.

  18. Теоретические основы прогнозирования коррозионной стойкости многослойных систем покрытий

    OpenAIRE

    Виноградова, С.; Кайдриков, Р.; Журавлев, Б.

    2011-01-01

    Описаны закономерности коррозионного поведения многослойных систем покрытий в атмосферных условиях. Проведен анализ электрохимических методов коррозионных испытаний и показаны преимущества кулонометрического метода для прогнозирования срока службы покрытий.The regularity of corrosion behavior of multilayer systems of coatings in atmospheric conditions is described. The analysis of electrochemical methods of corrosion tests was conducted. The advantages of coulometry method for forecasting ser...

  19. Carbon Dioxide, Hydrographic, and Chemical Data Obtained During the R/V John V. Vickers Cruise in the Pacific Ocean (WOCE Section P13, NOAA CGC92 Cruise, August 4 - October 21, 1992)

    Energy Technology Data Exchange (ETDEWEB)

    Kozyr, A.

    2001-01-11

    This data documentation discusses the procedures and methods used to measure total carbon dioxide (TCO{sub 2}) and total alkalinity (TALK) at hydrographic stations during the R/V John V. Vickers oceanographic cruise in the Pacific Ocean (Section P13). Conducted as part of the World Ocean Circulation Experiment (WOCE) and the National Oceanic and Atmospheric Administration's Climate and Global Change Program, the cruise began in Los Angeles, California, on August 4, 1992, with a transit line (Leg 0) to Dutch Harbor, Alaska. On August 16, the ship departed Dutch Harbor on Leg 1 of WOCE section P13. On September 15, the R/V John V. Vickers arrived in Kwajalein, Marshall Islands, for emergency repairs, and after 11 days in port departed for Leg 2 of Section P13 on September 26. The cruise ended on October 21 in Noumea, New Caledonia. Measurements made along WOCE Section P13 included pressure, temperature, salinity [measured by a conductivity, temperature, and depth sensor (CTD)], bottle salinity, bottle oxygen, phosphate, nitrate, nitrite, silicate, chlorofluorocarbons (CFC-11, CFC-12), TCO{sub 2} , and TALK. The TCO{sub 2} was measured by coulometry using a Single-Operator Multiparameter Metabolic Analyzer (SOMMA). The overall precision and accuracy of the analyses was {+-}2 {micro}mol/kg. Samples collected for TALK were measured by potentiometric titration; precision was {+-}2 {micro}mol/kg. The CO{sub 2} -related measurements aboard the R/V John V. Vickers were supported by the U.S. Department of Energy. The WOCE Section P13 data set is available free of charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center. The NDP consists of two oceanographic data files, two FORTRAN 90 data-retrieval routine files, a documentation file, and this printed report, which describes the contents and format of all files as well as the procedures and methods used to obtain the data. Instructions on how to access the data are provided.

  20. Rock magnetic signature of paleoenvironmental changes in the Izu Bonin rear arc over the last 1 Ma

    Science.gov (United States)

    Kars, Myriam; Vautravers, Maryline; Musgrave, Robert; Kodama, Kazuto

    2015-04-01

    During April and May 2014, IODP Expedition 350 drilled a 1806.5 m deep hole at Site U1437 in the Izu-Bonin rear arc, in order to understand, among other objectives, the compositional evolution of the arc since the Miocene and track the missing half of the subduction factory. The good recovery of mostly fine grained sediments at this site enables a high resolution paleontological and rock magnetic studies. Particularly, variations in magnetic properties and mineralogy are well documented. Natural remanent magnetization and magnetic susceptibility vary with a saw-tooth pattern. Routine rock magnetic measurements performed on about 400 samples in the first 120 meters of Hole U1437B showed that pseudo single domain to multidomain magnetite is the main carrier of the remanence. The origin of magnetite is likely detrital. The magnetic susceptibility variations depend on many factors (e.g. lithology, magnetic mineralogy, and also dilution by the carbonate matrix). The magnetic susceptibility is also used as a proxy, at first order, for magnetic minerals concentration. In order to highlight changes in magnetic minerals concentration, it's necessary to correct for the carbonate dilution effect. Onboard and onshore carbonate measurements by coulometry show that the carbonate content of the samples can be up to ~60%. About 70 samples were measured onshore. After correcting the susceptibility by the carbonate content measured on the same samples, it appears that the pattern of the magnetic susceptibility before and after correction is similar. Then the magnetic susceptibility variations do not result from carbonate dilution but reflect fluctuating influx of the detrital sediment component. The delta O18 variations obtained on foraminifers (N. dutertrei) show MIS 1 to MIS 25 over the studied interval covering the last 1 Ma (see Vautravers et al., this meeting). Rock magnetic properties, concentration and grain size variations of the magnetic minerals will be compared to

  1. Diaphragm-free cell for trace determination of water based on the karl Fischer reaction using continuous coulometric titration.

    Science.gov (United States)

    Cedergren, A; Jonsson, S

    1997-08-01

    A new type of diaphragm-free coulometric cell for continuous coulometric Karl Fischer titrations of water in the range 0.1-1000 μg is described. The relative standard deviation obtained for titrations of 1 μg amounts of water was typically 1%. The background due to diffusion of water from the air was normally in the range 0.3-0.9 μg of water min(-1) depending on environmental humidity. The variation in the background was normally ±0.01 μg min(-1). The construction makes it possible, at any time in a sequence of titrations, to renew the catholyte by means of a Teflon plunger inside the cathode compartment. In this way, the interference effects caused by oxidizable reduction products of methyl sulfite which are formed at the cathode can be controlled in a very simple way. These products are rapidly eliminated by means of a normal titration before a new titration starts. The need for this draining step differs depending on the type of reagent used. The coulometric titration system makes use of true potentiometric end-point detection, and this principle makes it possible to control the iodine level at the end-point at much lower levels as compared with commercial instrumentation. The analytical advantages gained by this option are demonstrated for the determination of water in ethylenediamine, a task which was found to be impossible when using end-point concentrations in the range (3-7) × 10(-5) M, which is typical for the bipotentiometric indicating system used in commercial instruments. Recovery rates in the range 100-102% were obtained and are shown to be dependent on the type of reagent used. The most accurate results were obtained for an imidazole-buffered methanolic reagent in which the concentration of sulfur dioxide was kept relatively low (0.10 M). The diaphragm-free cell described was shown to be compatible with all of the commercial reagents (designed for coulometry) investigated, including the well-known Hydranal products Coulomat A, AK, AG, AG-H, and

  2. Development of Paeonol Purity Reference Material and Method of Valuation%丹皮酚化学纯度标准物质研制与定值分析方法研究

    Institute of Scientific and Technical Information of China (English)

    徐维盛; 杨德智; 张丽; 杨宁; 马辰; 吕扬

    2011-01-01

    Objective To develop the paeonol purity reference material which has measurement traceability and high accuracy, and establish an effective method of valuation. Methods The paeonol purity reference material was studied on the basis of National Standard Material technical specification requirements. The homogeneity and stability test were measured by HPLC. The purity and uncertainty evaluation of the substance was measured by the peak area normalization method of HPLC and coulometry method. Results The paeonol purity reference material developed in this study conforms to the technical requirements of national primary standard reference material. The purity value and uncertainty evaluation of paeonol was (99. 87 ± 0.35)% (k = 2, P= 0.95). Conclusion The method established in our study was proved to be rapid, accurate and reliable, and was successfully applied to the purity value and uncertainty evaluation of paeonol purity reference material. It can provide the characteristic value transfer function.%目的 研制我国具有可溯源性高准确度量值的丹皮酚化学纯度标准物质,并建立有效定值分析方法 .方法 依据我国一级标准物质研制技术规范与有关技术文件,制备丹皮酚化学纯度标准物质,采用高效液相色谱(HPLC)法进行均匀性检验与稳定性考察;采用高效液相色谱技术面积归一化法与溴库伦滴定法对丹皮酚化学纯度标准物质联合定值.结果 研制的丹皮酚化学纯度标准物质符合我国有证标准物质要求,标准值与不确定度评估值为(99.87±0.35)%(k=2,P=0.95).结论 该实验研制的丹皮酚化学纯度标准物质与建立的联合定值方法 可实现对其化学纯度的定值与不确定度评估,方法 具有快速、准确的特点,提供了量值传递功能.

  3. PHOTO-ELECTROCHEMICAL QUANTUM EFFICIENCY OF TiO2 THIN FILMS : EFFECT OF CRISTAL STRUCTURE, PLASMA HYDROGENATION AND SURFACE PHOTOETCHING

    Directory of Open Access Journals (Sweden)

    E TEYAR

    2007-12-01

    Full Text Available The use of semi-conducting materials in the photoelectrochemical detoxification of water became a very important research field. For this purpose, TiO2 nanostructures thin films with size of 18 nm to 45nm have been synthesized at low temperature. It is found by means of cyclic voltametry and coulometry measurements that the best photoelectrochemical quantum efficiency under UV monochromatic light with a wavelength of 365 nm and a solution of NaOH 0.1N is obtained in the case of thermal oxidation deposition method which can reach 28% compared to ultrasonic spray and dip coating methods of which the quantum is less than 20%. The crystal structure has an influence on the photo-degradation of methanol. The crystal structure which is recommended for this task is the anatase one, especially in the dipping case when the quantum increases after addition of methanol more than twice compared to the solution of NaOH without methanol. The photoelectrochemical quantum efficiency of these films is related to the number of dips and annealing under air at 550°C during one hour. The annealing has no effect on the quantum efficiency of the films, but decreases there photocatalytic activity as showed by the measure of the photocurrent related to methanol photodegradation. The annealing has no effect on the crystal structure of the material. The impedance spectroscopy of six dips deposited films with and without methanol shows that the annealing increases the doping and weakly decreases the film quantum efficiency. This implies, the importance of surface morphology which the rough is decreasing as showed by scanning electron microscopy. The effect of the precursor concentration in ethanol have been investigated by using films, synthesized at T=550°C. The quantum efficiency increases weakly according the precursor concentration. It tends towards a saturation at great concentrations of precursor. In Na OH with methanol added, it passes by a maximum at

  4. Detection, characterization and quantification of inorganic engineered nanomaterials: A review of techniques and methodological approaches for the analysis of complex samples

    Energy Technology Data Exchange (ETDEWEB)

    Laborda, Francisco, E-mail: flaborda@unizar.es; Bolea, Eduardo; Cepriá, Gemma; Gómez, María T.; Jiménez, María S.; Pérez-Arantegui, Josefina; Castillo, Juan R.

    2016-01-21

    The increasing demand of analytical information related to inorganic engineered nanomaterials requires the adaptation of existing techniques and methods, or the development of new ones. The challenge for the analytical sciences has been to consider the nanoparticles as a new sort of analytes, involving both chemical (composition, mass and number concentration) and physical information (e.g. size, shape, aggregation). Moreover, information about the species derived from the nanoparticles themselves and their transformations must also be supplied. Whereas techniques commonly used for nanoparticle characterization, such as light scattering techniques, show serious limitations when applied to complex samples, other well-established techniques, like electron microscopy and atomic spectrometry, can provide useful information in most cases. Furthermore, separation techniques, including flow field flow fractionation, capillary electrophoresis and hydrodynamic chromatography, are moving to the nano domain, mostly hyphenated to inductively coupled plasma mass spectrometry as element specific detector. Emerging techniques based on the detection of single nanoparticles by using ICP-MS, but also coulometry, are in their way to gain a position. Chemical sensors selective to nanoparticles are in their early stages, but they are very promising considering their portability and simplicity. Although the field is in continuous evolution, at this moment it is moving from proofs-of-concept in simple matrices to methods dealing with matrices of higher complexity and relevant analyte concentrations. To achieve this goal, sample preparation methods are essential to manage such complex situations. Apart from size fractionation methods, matrix digestion, extraction and concentration methods capable of preserving the nature of the nanoparticles are being developed. This review presents and discusses the state-of-the-art analytical techniques and sample preparation methods suitable for

  5. Formation of aquatic Th(IV) colloids and stabilization by interaction with Cm(III)/Eu(III).

    Science.gov (United States)

    Yun, Jong-Il; Kim, Maria-Anna; Panak, Petra J; Kim, Jae-Il; Fanghänel, Thomas

    2006-03-23

    The present investigation is to ascertain under what conditions actinide ions undergo aggregation via oxo-bridging to form stable colloidal species. Eu and Th are taken for this purpose as trivalent and tetravalent actinide homologue ions, respectively. For verification of the effects of impurities in chemicals on the actinide colloid generation, pH is adjusted either by a conventional acid-base titration or by coulometry without addition of NaOH. The colloid generation is monitored by highly sensitive laser-induced breakdown detection in varying pH from 3 to 7, first in dilute Eu and Th solutions separately and then in a mixture of both, all in 0.5 M HCl/NaCl. The formation of stable colloids is observed particularly in a mixed solution of Eu and Th, suggesting that aggregation via mutual oxo-bridging of trivalent and tetravalent metal ions results in surface polarization, leading to stable hydrophilic particles of 20-30 nm in diameter. When Eu is replaced by Cm in the mixed solution in favor of the high fluorescence intensity of the latter, the chemical speciation is determined on colloid-borne Cm by time-resolved laser fluorescence spectroscopy. Two different colloid-borne Cm species, oxo-bridged with Th, are identified: a minor amount at 598.0 nm (denoted as Cm-Th(1)) and a major amount at 604.8 nm (Cm-Th(2)). The former is found as a transitional state, which converts to the latter with increasing pH and prevails at pH > 5.5. Both colloid-borne species (Cm-Th) are distinctively different from hydrolyzed Cm or its carbonate complexes with respect to their fluorescence peak positions and lifetimes. In conclusion, a mixed oxo-bridging of trivalent and tetravalent actinides elicits the generation of stable colloids, whereas individual ions in their pure state form colloids under oversaturation at near neutral pH only as a transitional state for precipitation.

  6. Utilización de técnicas acopladas de análisis térmico TG-DSC-QMSFTIR en la caracterización de arcillas y composiciones cerámicas utilizadas en la fabricación de baldosas cerámicas. Cuantificación de compuestos de carbono

    Directory of Open Access Journals (Sweden)

    Gómez, M. P.

    2007-10-01

    Full Text Available In this study, a work methodology has been developed for t evolved gas analysis (EGA in clay raw materials and ceramic compositions used in ceramic tile manufacture using coupled thermal analysis techniques (TG-DSC-QMS-FTIR. The different types of gases (CO2, CO, NOx, F, SOx evolving from these raw materials during a thermal cycle up to a peak temperature of 1200ºC were characterised. The possibility of using this calorimeter for the quantification of the CO2 gases evolving from the organic and inorganic carbon (carbonates present in the studied clay materials was also evaluated. The measurements were validated with different reference materials, and the results were compared with those obtained with other analysis techniques, such as thermogravimetry (TG, calcimetry, and coulometry. The thermal analysis technique (TG-DSC-QMS-FTIR is a suitable technique for analysing evolved gases with low uncertainties for carbon compounds quantification. Furthermore, the methodology allows the mineralogical origin identification of the elements present in the evolved gases.

    En el presente estudio se ha desarrollado una metodología de trabajo para el análisis de emisiones gaseosas (EGA en materias primas arcillosas y composiciones cerámicas utilizadas en la fabricación de baldosas cerámicas mediante técnicas acopladas de análisis térmico (TG-DSC-QMS-FTIR. Se caracterizaron los distintos tipos de emisiones (CO2, CO, NOx, F, SOx que se emiten durante un ciclo térmico hasta una temperatura máxima de 1200ºC. Asimismo, se evaluó la posibilidad de la utilización de la técnica para la cuantificación de dichas emisiones. En concreto se ha realizado la cuantificación de emisiones de CO2 procedentes de la presencia de carbono orgánico e inorgánico en materiales arcillosos. Se han validado las medidas con distintos materiales de referencia y se han comparado los resultados con los obtenidos con otras técnicas de análisis, tales como la

  7. Calcification rates of the Caribbean reef-building coral Siderastrea siderea adversely affected by both seawater warming and CO2-induced ocean acidification

    Science.gov (United States)

    Horvath, K. M.; Connolly, B. D.; Westfield, I. T.; Chow, E.; Castillo, K. D.; Ries, J. B.

    2013-05-01

    The Intergovernmental Panel on Climate Change (IPCC) predicts that atmospheric pCO2 will increase to ca. 550-950 ppm by the end of the century, primarily due to the anthropogenic combustion of fossil fuels, deforestation, and cement production. This is predicted to cause SST to increase by 1-3 °C and seawater pH to decrease by 0.1-0.3 units. Laboratory studies have shown that warming depresses calcification rates of scleractinian corals and that acidification yields mixed effects on coral calcification. With both warming and ocean acidification predicted for the next century, we must constrain the interactive effects of these two CO2-induced stressors on scleractinian coral calcification. Here, we present the results of experiments designed to assess the response of the scleractinian coral Siderastrea siderea to both ocean warming and acidification. Coral fragments (12/tank) were reared for 60 days under three temperatures (25.1± 0.02 °C, 28.0± 0.02 °C, 31.8± 0.02 °C) at near modern pCO2 (436 ± 7) and near the highest IPCC estimate for atmospheric pCO2 for the year 2100 AD (883 ± 16). Each temperature and pCO2 treatment was executed in triplicate and contained similarly sized S. Siderea fragments obtained from the same suite of coral colonies equitably distributed amongst the nearshore, backreef, and forereef zones of the Mesoamerican Barrier Reef System off the coast of southern Belize. Individual coral fragments were hand fed Artemia sp. to satiation twice weekly. Weekly seawater samples (250 ml) were collected and analyzed for dissolved inorganic carbon via coulometry and total alkalinity via closed-cell potentiometric titration. Seawater pCO2, pH, carbonate ion concentration, bicarbonate ion concentration, aqueous CO2, and aragonite saturation state (ΩA) were calculated with the program CO2SYS. Under near-modern atmospheric pCO2 of ca. 436 ± 7 ppm, seawater warming from 25 to 28 to 32°C caused coral calcification rates (estimated from change in

  8. Organic-Carbon Sequestration in Soil/Sediment of the Mississippi River Deltaic Plain - Data; Landscape Distribution, Storage, and Inventory; Accumulation Rates; and Recent Loss, Including a Post-Katrina Preliminary Analysis (Chapter B)

    Science.gov (United States)

    Markewich, Helaine W.; Buell, Gary R.; Britsch, Louis D.; McGeehin, John P.; Robbins, John A.; Wrenn, John H.; Dillon, Douglas L.; Fries, Terry L.; Morehead, Nancy R.

    2007-01-01

    Soil/sediment of the Mississippi River deltaic plain (MRDP) in southeastern Louisiana is rich in organic carbon (OC). The MRDP contains about 2 percent of all OC in the surface meter of soil/sediment in the Mississippi River Basin (MRB). Environments within the MRDP differ in soil/sediment organic carbon (SOC) accumulation rate, storage, and inventory. The focus of this study was twofold: (1) develop a database for OC and bulk density for MRDP soil/sediment; and (2) estimate SOC storage, inventory, and accumulation rates for the dominant environments (brackish, intermediate, and fresh marsh; natural levee; distributary; backswamp; and swamp) in the MRDP. Comparative studies were conducted to determine which field and laboratory methods result in the most accurate and reproducible bulk-density values for each marsh environment. Sampling methods included push-core, vibracore, peat borer, and Hargis1 sampler. Bulk-density data for cores taken by the 'short push-core method' proved to be more internally consistent than data for samples collected by other methods. Laboratory methods to estimate OC concentration and inorganic-constituent concentration included mass spectrometry, coulometry, and loss-on-ignition. For the sampled MRDP environments, these methods were comparable. SOC storage was calculated for each core with adequate OC and bulk-density data. SOC inventory was calculated using core-specific data from this study and available published and unpublished pedon data linked to SSURGO2 map units. Sample age was estimated using isotopic cesium (137Cs), lead (210Pb), and carbon (14C), elemental Pb, palynomorphs, other stratigraphic markers, and written history. SOC accumulation rates were estimated for each core with adequate age data. Cesium-137 profiles for marsh soil/sediment are the least ambiguous. Levee and distributary 137Cs profiles show the effects of intermittent allochthonous input and/or sediment resuspension. Cesium-137 and 210Pb data gave the most

  9. Lithographically patterned nanowire electrodeposition

    Science.gov (United States)

    Xiang, Chengxiang

    Lithographically patterned nanowire electrodeposition (LPNE) is a new method for fabricating polycrystalline metal nanowires using electrodeposition. In LPNE, a sacrificial metal (M1 = silver or nickel) layer, 5 - 100 nm in thickness, is first vapor deposited onto a glass, oxidized silicon, or Kapton polymer film. A photoresist (PR) layer is then deposited, photopatterned, and the exposed Ag or Ni is removed by wet etching. The etching duration is adjusted to produce an undercut ≈300 nm in width at the edges of the exposed PR. This undercut produces a horizontal trench with a precisely defined height equal to the thickness of theM1 layer. Within this trench, a nanowire of metal M2 is electrodeposited (M2 = gold, platinum, palladium, or bismuth). Finally the PR layer and M1 layer are removed. The nanowire height and width can be independently controlled down to minimum dimensions of 5 nm (h) and 11 nm (w), for example, in the case of platinum. These nanowires can be 1 cm in total length. We measure the temperature-dependent resistance of 100 um sections of Au and Pd wires in order to estimate an electrical grain size for comparison with measurements by X-ray diffraction and transmission electron microscopy. Nanowire arrays can be postpatterned to produce two-dimensional arrays of nanorods. Nanowire patterns can also be overlaid one on top of another by repeating the LPNE process twice in succession to produce, for example, arrays of low-impedance, nanowirenanowire junctions. The resistance, R, of single gold nanowires was measured in situ during electrooxidation in aqueous 0.10 M sulfuric acid. Electrooxidation caused the formation of a gold oxide that is approximately 0.8 monolayers (ML) in thickness at +1.1 V vs saturated mercurous sulfate reference electrode (MSE) based upon coulometry and ex situ X-ray photoelectron spectroscopic analysis. As the gold nanowires were electrooxidized, R increased by an amount that depended on the wire thickness, ranging from